Theme Guides
Last updated July 2026
Themes are how people actually think about portfolios. Not “will this ticker go up” but “is AI infrastructure still the right place to be”, “does my income side need more dividend growth”, “am I exposed to defense modernization at all”. Each theme below lists every stock that fits, the ETFs commonly used as passive proxies, and how to build a portfolio around it in Walnut.
Short answer
Thematic investing means building part of a portfolio around a long-term idea rather than a single stock or a sector label. Each theme on this page is a thesis with the stocks and ETFs that express it. The page lists every company that fits the idea, starts them equal-weighted so no single name dominates, shows the ETFs people use as passive proxies, and lets you turn the thesis into a portfolio you fund through your own broker. Themes work best as satellites sized deliberately around a diversified core, not as an entire portfolio. This is educational information, not a recommendation.
What is thematic investing?
Thematic investing organizes a portfolio around ideas instead of tickers. Rather than starting from “which stock should I buy”, you start from a conviction about how the world is changing, then hold the group of companies that stand to express that change. The unit of the decision is the thesis, not the individual name. If you believe AI compute demand will keep growing for years, that belief is more durable and more diversifiable than a bet on any one chipmaker, and it points naturally to a group of companies rather than a single one.
This is a different frame from the two most common ways people already invest. A broad index fund gives you the whole market and asks for no view at all. Picking a single stock takes a sharp view but concentrates the outcome on one company's specific risks. A theme sits between the two: it takes a deliberate view, an idea you can state in a sentence, but spreads it across the several companies that share the thesis, so a single earnings miss or management stumble does not sink the whole idea.
The themes collected here span the trends that are actually moving portfolios: AI infrastructure and the data center power and cooling that supports it, semiconductors, defense modernization, dividend growth for the income side of a portfolio, critical materials, robotics, nuclear and clean energy, and more. For the wider context on why investors group holdings this way, read our deeper guide on thematic investing.
How to invest in a theme
Once you have picked a theme, there are two practical ways to express it, and they trade convenience against control.
- Buy a thematic ETF. One purchase gives you diversified exposure to the idea, and the fund handles the holdings and rebalancing for you. The trade-offs are cost and precision: thematic ETFs usually carry higher expense ratios than broad-market funds, their holdings can drift from the pure thesis, and a fund often launches when a theme is already popular. Each theme page lists the ETF proxies people most commonly use so you can compare them.
- Assemble the individual stocks. Holding the names yourself lets you control exactly which companies and weights you own, leave out businesses whose fit you doubt, and avoid fund fees. The cost is effort: you research each name, decide the weights, and rebalance over time. This is where a portfolio helps, because it turns a list of tickers into a single tracked position with target weights.
Whichever path you take, size matters more than the entry. Themes concentrate on one idea, so they tend to swing harder than the broad market. Many investors treat a theme as a satellite: a smaller, deliberate tilt sized around a diversified core of broad holdings, rather than the center of the portfolio. That way a theme can add exposure to an idea you believe in without letting a single trend drive your whole result.
In Walnut, the workflow is direct: you describe the thesis in plain language, the AI assistant proposes five or six constituents with target weights, and you fund the portfolio through your own connected broker. You approve every order; Walnut never trades on your behalf. Walnut is informational, not an investment adviser.
How these themes are built
Each theme page starts from a written thesis and a clear inclusion test: a company earns a place in the theme only if its business genuinely expresses the idea, not because it is merely a large, well-known name in a nearby sector. That is why the AI infrastructure theme reaches past chipmakers into the industrials that build data-center power and cooling, and why a defense theme includes the specific primes and suppliers tied to modernization budgets rather than the whole industrials sector.
The constituents in every theme start equal-weighted, meaning each company begins with the same share of the portfolio. This is a deliberate default. A theme is a statement about an idea, not a claim that one specific company is the best way to play it, and equal weighting keeps any single name, especially the largest and most familiar, from quietly dominating the whole position. It also makes the performance chart on each page an honest read on the idea itself rather than a proxy for one mega-cap. Equal weighting is a starting point, not a rule: inside Walnut you set your own target weights, tilting toward the names you have the most conviction in.
Every theme page also carries a hypothetical performance line versus the S&P 500, the full roster of stocks with the rationale for each inclusion, and the ETF proxies for anyone who wants the idea as a single ticker. The stock and ETF names link through to their own guides, so you can drill from a theme into any one company and see which other themes it belongs to.
Themes versus sectors
It is easy to confuse a theme with a sector, but they answer different questions. A sector is an industry classification. The widely used GICS framework splits the market into eleven of them, technology, health care, financials, energy, and so on, grouping companies by the broad business they are in. Sectors describe the structure of the market.
A theme cuts across those lines. AI infrastructure, for instance, pulls semiconductors from technology, power and cooling builders from industrials, and grid names from utilities, companies scattered across three sectors that all express one thesis. A sector answers “what industry is this company in”; a theme answers “which idea does this company help me express”. The two are complementary lenses: spreading across sectors is a way to manage concentration risk, while a theme is a way to take a deliberate view. If you want to think in industry terms instead, see our guide on how to invest in sectors.
Browse the themes
Each theme below opens a full guide: the thesis, every stock that fits it, the ETF proxies, a hypothetical performance line versus the S&P 500, and a one-click way to build it as a portfolio.
AI infrastructure
20 stocksPicks and shovels of the AI buildout: GPUs, networking, foundries, and the software platforms training the largest models.
Data center power and cooling
9 stocksThe grid, switchgear, liquid cooling, and electrical contracting that AI data centers can't run without.
Semiconductors
18 stocksThe full chip stack: designers, foundries, equipment makers, materials suppliers, and packaging specialists.
Defense and modernization
5 stocksSoftware, sensors, and specialty materials at the center of US and allied defense buildouts.
Critical materials
4 stocksRare earths, specialty metals, and strategic materials at the center of supply chain reshoring.
Dividend growth
10 stocksCompanies that compound a growing dividend through cycles. The boring core of many long-term portfolios.
Consumer discretionary
6 stocksRetailers, marketplaces, and consumer brands tied to discretionary spending and trade-down dynamics.
Enterprise software
5 stocksCloud-native platforms running workflows, data, and AI agents inside large enterprises.
Infrastructure and reshoring
10 stocksBuilders, materials, and equipment behind the multi-year US infrastructure and reshoring buildout.
Agriculture
3 stocksInputs, equipment, and producers feeding the food system.
AI agents
7 stocksSoftware that plans and acts on its own: the model providers, enterprise platforms, and compute behind autonomous AI workflows.
Humanoid robotics
6 stocksGeneral-purpose robots for human environments: the AI brains, actuators, sensors, and automation expertise behind them.
Nuclear and SMR
7 stocksExisting-reactor operators, small modular reactor developers, and the uranium and engineering supply chain behind firm clean power.
Quantum computing
6 stocksQuantum processors and the software to program them: diversified research anchors plus speculative pure-play developers.
Cybersecurity
6 stocksProtecting networks, identities, and cloud workloads: subscription security platforms benefiting from consolidation and resilient budgets.
Cloud computing
6 stocksOn-demand compute, storage, and data: the hyperscale platforms plus the data and edge layers built on top.
Electric vehicles and batteries
6 stocksAutomakers, battery makers, lithium suppliers, and next-generation cells behind the shift to electric transport.
Space economy
7 stocksLaunch providers, satellite communications, lunar services, and the defense primes with large space divisions.
GLP-1 and obesity drugs
5 stocksMakers of GLP-1 medicines for diabetes and obesity: the dominant leaders plus the next-wave developers chasing improved drugs.
Uranium
5 stocksMiners and developers that supply nuclear fuel: established producers plus earlier-stage explorers leveraged to the uranium price.
Copper and electrification
5 stocksThe metal of the energy transition plus the equipment and grid companies that turn it into infrastructure.
Fintech and digital payments
7 stocksCard networks, digital-payment and neobroker platforms, and crypto-linked players riding the shift from cash to digital.
3D printing
9 stocksAdditive manufacturing companies: the printer hardware, materials, and on-demand parts services that build objects layer by layer instead of cutting or molding them.
Automation
11 stocksThe companies that automate factories and production lines: industrial robots, motion and control systems, machine vision, and the controllers that run modern manufacturing.
Biotech
12 stocksCompanies developing drugs, gene therapies, and genomic technologies, from large profitable biotechs to clinical-stage names.
Drones
9 stocksCompanies building military and commercial unmanned aerial systems, the autonomy and counter-drone tech around them, and the adjacent electric air-taxi makers.
Hydrogen and fuel cells
8 stocksFuel-cell makers, electrolyzer builders, and the industrial-gas giants that actually move most of the world's hydrogen today.
Metaverse, VR and AR
8 stocksCompanies building the hardware, chips, engines, and content for immersive virtual and augmented reality, from headset makers to the platforms where digital worlds get built.
Real assets
12 stocksCompanies tied to tangible, inflation-sensitive assets: real estate, infrastructure, commodities and materials, energy, and precious metals.
Silver and precious metals
11 stocksMiners, streamers, and royalty companies leveraged to silver and gold prices, plus the ETF proxies investors use for precious-metals exposure.
Travel and tourism
12 stocksThe companies people spend on when they take a trip: online travel platforms, hotels, cruise lines, airlines, and casino resorts.
Water
11 stocksThe regulated utilities, pumps and pipes, and treatment and testing companies that move, clean, and measure the world's water supply.
Technology
18 stocksThe broad technology sector: software, semiconductors, internet platforms and the hardware underneath them.
Energy
15 stocksOil and gas producers, refiners, midstream pipelines and the utilities powering the grid.
Healthcare
15 stocksPharmaceutical makers, medical device companies, insurers and the diagnostics behind them.
Defensive stocks
14 stocksConsumer staples, utilities and healthcare names whose demand holds up when the economy weakens.
Oil stocks
14 stocksCrude producers, refiners and the oilfield services companies that drill and complete the wells.
Financial stocks
13 stocksBanks, payment networks, exchanges, asset managers and insurers.
Bank stocks
12 stocksMoney-centre banks, regional lenders and brokerages that earn on the spread between deposits and loans.
Mining stocks
13 stocksDiversified miners and metals producers digging copper, iron ore, gold and industrial materials.
REITs
11 stocksReal estate investment trusts owning data centres, towers, warehouses, housing and retail property.
Retail stocks
10 stocksBig-box chains, specialty retailers and restaurant groups selling directly to consumers.
Utility stocks
8 stocksRegulated electric and water utilities, plus the independent power producers supplying data-centre demand.
Solar stocks
8 stocksPanel manufacturers, inverter makers, residential installers and utility-scale developers.
Pharmaceutical stocks
10 stocksLarge drug makers whose value rests on approved products, patent life and the pipeline behind them.
5G stocks
11 stocksNetwork equipment makers, chip designers, tower operators and the carriers running the networks.
Steel stocks
11 stocksIntegrated mills, electric-arc producers and the diversified miners feeding them iron ore.
Blockchain stocks
10 stocksCrypto exchanges, bitcoin miners, treasury holders and the chipmakers supplying them.
Auto stocks
9 stocksLegacy carmakers, electric-vehicle manufacturers and the suppliers feeding both.
Natural gas stocks
9 stocksGas producers, LNG exporters and the midstream pipelines moving it.
Rare earth stocks
8 stocksMiners and processors of the critical minerals behind magnets, batteries and defence systems.
Gaming stocks
6 stocksConsole and PC platform owners, chipmakers and the hardware behind interactive entertainment.
Streaming stocks
7 stocksSubscription video platforms, studios and the connected-TV distributors around them.
E-commerce stocks
6 stocksOnline marketplaces, direct-to-consumer platforms and the software running online stores.
Social media stocks
5 stocksAdvertising-funded social platforms and the search and content networks alongside them.
Gene editing stocks
5 stocksCRISPR and gene therapy developers working on treatments that edit DNA directly.
Lithium stocks
6 stocksLithium producers, battery makers and the solid-state developers behind next-generation cells.
Casino and gambling stocks
9 stocksCasino operators, online sportsbooks and the gaming REITs that own the properties.
Geothermal stocks
4 stocksGeothermal power developers and the oilfield services companies drilling the wells.
Clean energy stocks
12 stocksRenewable generation, grid equipment, storage and the utilities building the transition.
Drone stocks
6 stocksMilitary and commercial drone makers, eVTOL developers and counter-drone systems.
Gold stocks
5 stocksGold miners and royalty companies, the leveraged equity way to hold exposure to the metal.
Materials
11 stocksIndustrial gases, specialty chemicals, aggregates and the steel and copper inputs behind construction.
Real estate stocks
8 stocksProperty owners across data centres, towers, warehouses, housing and retail, mostly structured as REITs.
Cannabis stocks
6 stocksLicensed producers and cannabis-focused property owners in a sector defined by regulation.
Dividend stocks
11 stocksEstablished, cash-generative companies that return a meaningful share of profit to shareholders as cash.
Value stocks
12 stocksEstablished businesses trading at low multiples of earnings, cash flow or assets relative to the market.
Growth stocks
16 stocksCompanies growing revenue well above the market, priced on what they are expected to earn rather than what they earn now.
Blue chip stocks
17 stocksThe largest, most established companies in the market, held for durability rather than for a specific theme.
ESG stocks
11 stocksCompanies screened on environmental, social and governance criteria alongside their financial characteristics.
Momentum stocks
6 stocksStocks that have outperformed recently, held on the tendency for relative strength to persist.
Small and mid cap stocks
7 stocksSmaller listed companies with more room to grow, less analyst coverage and considerably more volatility.
FAQ
What is thematic investing?
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Thematic investing means building part of a portfolio around a long-term idea or trend rather than around a sector label or an index. Instead of asking whether one ticker will go up, you pick a thesis you believe in, such as AI infrastructure or defense modernization, and hold the group of companies that actually express it. Each theme page here lists every stock that fits the thesis, the ETFs commonly used as passive proxies, and how to build it as a portfolio.
How do I invest in a theme?
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There are two common paths. You can buy a thematic ETF and get the whole idea in one ticker, accepting whatever holdings and weights the fund uses, or you can assemble the individual stocks yourself and control exactly which names and weights you hold. Each theme page shows both: the stocks that fit the thesis and the ETF proxies. In Walnut you describe the thesis, the AI proposes constituents and weights, and you fund it through your own broker.
Are thematic ETFs worth it?
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Thematic ETFs are convenient because one purchase gives you diversified exposure to an idea, but they come with trade-offs: expense ratios are usually higher than broad-market funds, holdings can drift from the pure thesis, and popular themes sometimes launch funds near a peak in enthusiasm. They can be a reasonable way to express a theme passively. Whether they suit you depends on your costs, time horizon, and how much control you want. This is general information, not a recommendation.
How much of my portfolio should be thematic?
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Many people treat themes as satellites around a diversified core rather than as the whole portfolio. A common framing is to keep the majority in broad, low-cost holdings and size individual themes as smaller tilts you can stand to see swing. There is no single correct percentage; it depends on your goals, time horizon, and tolerance for concentration. Themes tend to be more volatile than the broad market, so sizing them deliberately matters.
What is the difference between a theme and a sector?
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A sector is an industry classification, such as technology or health care, that groups companies by what they broadly do. A theme cuts across sectors and groups companies by a shared idea. AI infrastructure, for example, pulls in semiconductors, industrials that build data-center power and cooling, and utilities, names that live in different sectors but all express one thesis. Sectors describe the market's structure; themes describe an investment idea.
Are these themes recommendations to buy?
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No. Theme membership is descriptive, not prescriptive. Each page explains what a theme is, which companies fit its thesis, and how you might express it, but nothing on these pages is a recommendation to buy or sell any security. Walnut is informational, not an investment adviser. You connect your own broker and approve every order yourself.
Have a thesis we haven't named?
Walnut's AI assistant turns any plain-language thesis into a 5-to-6 stock portfolio. You don't need us to have a theme page already; describe what you believe in, the AI proposes constituents, and you fund it through your broker.
Create a free Walnut accountWalnut is informational, not investment advice. Theme membership is descriptive, not prescriptive; nothing on this page should be read as a recommendation to buy or sell any security. Always verify current financials and your own circumstances before investing.