Any stock theoretically holds the potential to make you a millionaire. But few actually do. Stocks with the greatest likelihood of building fortunes tend to have small market caps and huge market opportunities. 

Cannabis definitely offers a huge market opportunity. The global cannabis market could expand close to tenfold over the next 10 to 15 years. Many players in the cannabis industry remain small and have a lot of room to grow as the market opportunities unfold. Which marijuana stocks can investors buy right now that hold the potential to be millionaire-makers? Here are three that I think are at the top of the list.

Cannabis leaf on top of a pile of $100 bills

Image source: Getty Images.

1. Valens 

Valens (OTC:VLNCF) is a virtual lock to profit in a big way as the global cannabis market expands, in my view. The company provides services to extract cannabinoids such as CBD and THC from cannabis plants.

It's a pretty safe bet that the demand for cannabis extraction will soar over the next few years. The Cannabis 2.0 cannabis derivatives market in Canada is just getting started. Products including cannabis-infused beverages and foods as well as vapes are expected to rack up billions of dollars in sales. In the U.S., the legalization of hemp in late 2018 should drive increased demand for products containing hemp-derived CBD.

Valens is set to be a major winner in Canada's Cannabis 2.0 market and could make significant headway into the U.S. market, too. It boasts the highest extraction capacity in the industry. The company's customers include many of the biggest names in the business --Canopy Growth, HEXO, Organigram (NASDAQ:OGI), Tilray, and more. With a market cap of around $350 million, I think that Valens should deliver massive returns over the next decade.

2. Organigram

One of Valens' customers should also achieve tremendous success in the not-too-distant future. Organigram isn't the largest cannabis producer in Canada, but it's arguably the best.

Most of the major Canadian cannabis producers are struggling to establish a clear path to profitability. Organigram, though, appears to be in a good position to become profitable after its stellar fiscal 2020 first-quarter results announced a few weeks ago. The company's low cultivation costs and fiscal discipline put Organigram in the top tier of cannabis producers. Its market cap of around $450 million -- lower than most of its key rivals -- makes Organigram a better bargain.

Several factors should fuel Organigram's growth. The company's sales should soar as the Cannabis 2.0 market in Canada picks up steam. Ontario, Canada's most heavily populated province, is opening more retail stores throughout 2020. I also wouldn't be surprised if a large consumer packaged goods company partners with Organigram, opening the door for the cannabis producer to more effectively reach the global cannabis market.   

3. Innovative Industrial Properties

With a market cap of over $1.2 billion, Innovative Industrial Properties (NYSE:IIPR) is a good bit bigger than Valens and Organigram. However, I think that IIP remains small enough to provide huge returns over the next few years -- just as it has done over the last three years.

IIP is the largest cannabis-focused real estate investment trust (REIT). It acquires properties and leases them to medical cannabis operators in deals that free up cash flow for tenants and provides an ongoing revenue stream to IIP. So far, the company has 48 properties in 15 states. But that number will almost certainly continue to grow rapidly.

There are currently 18 states with legal medical cannabis markets that IIP hasn't entered yet and more states are likely to vote to legalize medical cannabis in November. The cannabis markets in many of the states were the company already operates are still in their early stages. IIP also has a big opportunity in expanding its relationships with existing multistate cannabis operators such as Cresco Labs

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.