Who invented WhatsApp?

Jan Koum is a Ukrainian American computer programmer. In January 2009, Koum bought an iPhone and realized that the then seven-month-old App Store was about to spawn a whole new industry of apps. He visited his friend Alex Fishman and the two talked for hours about Koum's idea for an app. Koum almost immediately chose the name WhatsApp because it sounded like "what's up", and a week later on his birthday, February 24, 2009, he incorporated WhatsApp Inc. in California.