Bill Gates took to Twitter Monday in a series of tweets to answer a question he is asked most frequently during graduation season: Career advice.

One of the most surprising tweets was when Bill admitted he would pick a career in AI (artificial intelligence), energy, or biosciences if he were starting out in today's world.

He told graduates to surround themselves with people such as his wife, Melinda Gates. Bill said people like his wife "...challenge you, teach you, and push you to be your best self."

Bill said, like billionaire businessman Warren Buffett, he measures happiness by whether people close to him are happy and love him, and by the difference he makes for others.

He ended his advice by saying, "This is an amazing time to be alive. I hope you make the most of it."