Elon Musk, the world's richest man and now first-ever trillionaire, controls a lot of different businesses.Electric vehicles. Brain implants. Underground tunnels. A social media platform once called Twitter. And a rocket maker that blasted off its trading from Wall Street this week.Over time, more and more of these ventures have found themselves under the same roof. Musk merged SpaceX - which went public on Friday - with his artificial intelligence company xAI just earlier this year. But he still holds the CEO role at several corporations today, in addition to other various executive titles or ownership stakes.Here's a look at...