Warren Buffett’s Berkshire Hathaway (NYSE: BRK.A) (NYSE: BRK.B) is often considered a reliable stock for conservative long-term investors. The conglomerate is led by Warren Buffett, who famously said his favorite holding period for a stock is "forever.

Right now, his holding company, Berkshire Hathaway, is betting on two stocks that every investor should strongly consider. The long-term upside potential for both companies is truly impressive. Few companies have grown as quickly in recent years as Nu Holdings (NYSE: NU).

Nubank, Latin America’s largest fintech bank, has the ability to grow globally. A recent pullback in its parent company’s shares offers an attractive entry point.

While Cathie Wood, chief executive of Ark Investment Management, specializes in small- and midcap technology stocks, sometimes she goes for the megacaps. The idea presumably is to provide ballast for her funds,

Cathie Wood is well known for her aggressive investing style. She's poured billions of dollars into electric car manufacturers like Tesla and BYD, cryptocurrencies including Bitcoin, and dozens of other companies with massive upside potential -- but with plenty of downside potential,