Facebook is joining the fitness craze. Popular fitness-tracking app Moves announced that it will now be joining Facebook. This latest acquisition falls in line with Facebook's plans to create a mobile app empire.

Moves assured its users that it will remain a standalone fitness app, independent from the main Facebook app. Moves also said that currently, there are no plans to "commingle data with Facebook," which should assuage any user concerns about privacy.

Moves expressed excitement over its new partnership with Facebook, saying that Facebook's team will help improve the app, as well as extend Moves' reach, hopefully to a billion people. The company promised that the app will largely remain unchanged and reiterated its commitment to creating a simple, beautiful fitness-tracking diary app.

It's no mystery why Facebook has decided to buy Moves. Fitness wearables, apps and diaries are all the rage right now and Moves is one of the most appealing fitness apps out there. Moves has had more than four million downloads since it debuted last January and says that it has "millions" of active users. As fitness apps grow in popularity and more functional fitness wearables hit the market, Moves will only amass more users.

In turn, Moves will give Facebook more user data to analyze and capitalize upon with targeted advertisements.

Facebook CEO Mark Zuckerberg told the New York Times earlier this month that he plans on expanding Facebook's mobile app empire with a series of apps that, while related to Facebook, don't carry the Facebook brand name. Zuckerberg's plan is to turn Facebook into a mobile app powerhouse, with dozens of apps from different categories available for download.

Facebook's list of apps is growing steadily and now includes Instagram, WhatsApp, Paper, Facebook Messenger and Moves, in addition to the big blue app. So far, that strategy has investors very optimistic about Facebook, as do the company's very good quarterly earnings. Zuckerberg is just getting started, so expect to see a lot of app acquisitions from Facebook in the near future.