Facebook acquired WhatsApp, the mobile messaging startup, for $19 billion in cash and stock on February 19, 2014. This was Facebook's largest acquisition to date. WhatsApp had 450 million active users at the time and was growing rapidly, registering around 1 million new users per day. Facebook believed acquiring WhatsApp would help it strengthen its position in the mobile messaging market and capture the growth in mobile messaging, especially among younger users. The founders of WhatsApp, Jan Koum and Brian Acton, both had backgrounds in engineering and met while working at Yahoo. WhatsApp was their first major business venture together after leaving Yahoo.