Seeking to become a worldwide leader in messaging, Facebook on Wednesday announced that it would purchase cross-platform mobile messaging solution WhatsApp for an incredible $16 billion. And the value of the deal could rise to $19 billion if WhatsApp's employees remain with Facebook for four years.

The incredible acquisition deal was revealed in a US Securities and Exchange Commission (SEC) filing, which notes that WhatsApp will become a wholly owned subsidiary of Facebook. The social networking giant then further explained the deal.

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"Facebook has reached a definitive agreement to acquire WhatsApp, a rapidly growing cross-platform mobile messaging company, for a total of approximately $16 billion, including $4 billion in cash and approximately $12 billion worth of Facebook shares," a Facebook statement notes.

WhatsApp is available on Android, iPhone, Windows Phone, BlackBerry, and even Nokia Symbian phones. The service claims more than 450 million users, over 70 percent of which are considered "active" in that they use the service's mobile app each day. Usage is growing at a rate of more than 1 million new users per day.

WhatsApp maintains that nothing will change for its users.

"WhatsApp will remain autonomous and operate independently," WhatsApp Cofounder and CEO Jan Koum writes on the firm's corporate blog. "You can continue to enjoy the service for a nominal fee. You can continue to use WhatsApp no matter where in the world you are, or what smartphone you're using. And you can still count on absolutely no ads interrupting your communication. There would have been no partnership between our two companies if we had to compromise on the core principles that will always define our company, our vision, and our product."

Facebook reportedly offered to purchase a rival chat service, SnapChat, for $3 billion but was turned down. Facebook previously purchased Instagram for $1 billion