According to Chinese legend, the Emperor Shen Nong discovered tea in 2737 B.C.E., when a random tea leaf landed in a pot of water he was boiling in his garden. He drank the infusion, loved it, and set off on a mission to discover all the healing properties of the newly discovered plant. And we get to enjoy the benefits of that ancient accident today. For thousands of years, people have been drinking tea to ease stress, unwind and relax during tense times. But with so many teas touting calming powers, it’s hard to know what to look for. Here’s what you need to know.