AlphaGo is the first computer program to defeat a professional human Go player. In October 2015, it defeated Fan Hui, the reigning 3-times European champion, in an even match. In March 2016, it won 4-1 against Lee Sedol, one of the top professional players in the world. Go is a 2,500 year old game that has more possible positions than there are atoms in the universe. Consequently, it is 10^100 times more complex than chess.