King Tutankhamun is one of the most famous rulers who ever lived thanks to the 1922 discovery of the pharaoh’s tomb in Egypt’s Valley of the Kings. The find stirred the imaginations of millions who were fascinated by the boy king’s golden-masked mummy. (How was Tut's tomb discovered 100 years ago? Grit and luck.)

But what do we really know about Tut? Although many details of his reign remain lost to time, historians have spent years trying to piece together the pharaoh’s life and legacy. Here’s what they’ve learned—and the biggest questions that remain.