Want to do something risky, provocative, and fun? Invest in small-cap companies with big, bright futures. If you're wrong in your investment thesis, your principal could plummet. But if you're right, the sky's the limit. Let's look at two tiny companies that might be incredibly valuable down the road.

Silvergate Capital (NYSE:SI) is a small-cap bank at the epicenter of all the institutions trading various cryptocurrencies. And Ontrak (NASDAQ:OTRK) offers virtual coaching to people who have behavioral-health conditions and are looking for change. Here's why these two small caps are great stocks to own in 2021.

A giant clock, face mostly frosted, with hands moving to 2021

Image source: Getty Images.

1. Silvergate Capital facilitates the crypto craze

Opinions on cryptocurrencies vary -- to put it lightly. Warren Buffett calls these new currencies "rat poison squared," while Twitter and Square CEO Jack Dorsey thinks bitcoin will eventually supplant the dollar, the yen, and the euro. I have no dog in this fight, but I do think a lot of money can be made in this modern-day gold rush. And I don't mean by mining bitcoin. Instead, investors might want to invest in the bank that facilitates all the trading.

That's what Silvergate Capital does. Silvergate owns and operates the Silvergate Exchange Network (SEN). The bank doesn't hold any cryptocurrencies on its books -- its assets are all cash. Institutions that want to trade cryptocurrencies deposit dollars at Silvergate, and the bank transfers dollars internally between its various accounts. Through its SEN network, all the crypto trading platforms can quickly and easily transfer dollars to their institutional clients, 24/7.

This is free money for Silvergate -- the bank pays no interest on all these deposits. And Silvergate makes money in the traditional banking way, by collecting interest on all the cash deposited at the bank.

While bitcoin won't replace the dollar anytime soon, it's obviously an asset class now. It's like gold in that sense -- a vehicle for supply and demand. And that's why many large institutions, companies, and banks are holding and trading bitcoin and other cryptocurrencies. In the process, they're depositing more and more dollars at Silvergate.

This bank stock rose almost 315% over the past 12 months. Indeed, Silvergate is up about 50% since I wrote about it a little over two weeks ago. And yet it's still tiny for a financial stock, with a $1.24 billion market cap.

While the current boom in Silvergate stock is probably due to the rising price of bitcoin, a strong network effect makes the SEN more and more valuable, and increases the value of the bank as well. Expect a lot of volatility in 2021, as more investors discover this tiny bank that accumulates dollars while facilitating the demand to trade in cryptocurrencies.

2. Ontrak's growth story is just beginning

Ontrak is a virtual healthcare coach that helps people who are dealing with mental-health issues like depression or addiction. The company markets its solutions to health insurers. Since many people with mental-health issues don't seek treatment on their own, Ontrak relies on artificial intelligence to find people on each health plan who might benefit from its coaching.

These virtual nudges are extremely cost-effective for employers and health insurers. If addiction or other mental-health issues worsen, people can end up in rehab, an expensive proposition. Ontrak seeks to find and guide people on a health plan before their situations become acute; among its members, 97% have not received behavioral-health services in the last 12 months.

In a Humana case study, the average cost of providing healthcare was $30,000 a year prior to Ontrak. Adoption of the Ontrak program cut Humana's costs in half. Over two years Humana saved over $31,000 per insured, for a 370% return on investment. And the Ontrak programs are highly popular with insured people. The company's net promoter score (an attempt to measure word-of-mouth advertising) is 74, vastly higher than the average score of 4 for various other health plans.

Ontrak has signed up other major insurers, including Aetna and Cigna. Because of the pandemic, the onboarding of Cigna's insured patients has been delayed. Nonetheless, Ontrak is having fantastic growth: In the third quarter, it reported $24 million in revenue, up 172% from last year. Out of a pool of 144,000 insured people from its various partnerships, Ontrak has enrolled 14,345 in its program.

Demand is huge right now. The lockdown is causing a mini-pandemic of mental-health issues. Severe depression in the U.S. has skyrocketed, from 0.7% to 5.1% of the population, according to The Journal of the American Medical Association. Indeed, thanks to quarantines and stay-at-home orders, virtual healthcare has been all the rage this year. When Teladoc Health (NYSE:TDOC) announced that it was acquiring Livongo Health (a virtual healthcare company that specializes in diabetes management), Ontrak shares rose nearly 50% overnight, jumping from $39 to a high of $58 the next day. And there's plenty of room for this small cap to run higher in 2021.

Riding the pandemic wave

Ontrak and Silvergate Capital are two small caps that are riding very big waves right now. Both of these companies have an opportunity to grow substantially over the next few years. Profitable Silvergate makes lots of cash as institutions and hedge funds dip their toes into trading cryptocurrencies. And Ontrak is experiencing triple-digit revenue growth as health insurers look to intervene before mental-health issues become more dire (and more costly). Investors seeking outsize returns ought to read up on these two amazing stocks.