Jan Koum is the co-founder and former CEO of WhatsApp, which was acquired by Facebook for $19 billion in 2014. He grew up in Ukraine and immigrated to the US in 1992 where he worked various jobs before studying computer programming. He co-founded WhatsApp in 2009 and it grew extremely popular, catching the attention of Facebook founder Mark Zuckerberg. They met several times before Facebook acquired WhatsApp in 2014, making Koum a billionaire. He resigned from Facebook in 2018.