—Year founded: 2009.
—Company founders: Former Yahoo engineers Jan Koum (the current CEO) and Brian Acton.
—Headquarters: Mountain View, Calif.
—Number of employees: 55.
HOW IT WORKS:
—Download the app to phones running Android and iPhones, as well as BlackBerry, Windows and Nokia phones.
—Messages are sent over the Internet, to individual people or groups.
—One check mark next to a message means it's been delivered; two check marks means it's been seen.
—Price users pay for one year of service: 99 cents.
—Number of monthly WhatsApp users: 450 million.
—Number of people who use Facebook's mobile products, including Facebook Messenger and Instagram every month: nearly 950 million.
—Number of WhatsApp texts sent per day: 19 billion; texts received on the service per day: 34 billion.
—Number of daily voice messages sent with WhatsApp: 200 million; daily video messages: 100 million; daily photos: 600 million.