How to use FaceApp, the app that can age your face or swap your gender

In the era of the selfie, there's no shortage of apps that can make you better looking, turn you into a dog, or even swap your face onto someone else's.

Now, there's an app that can alter your gender entirely, age you, or add a smile to your face.

Called FaceApp, the app can take a selfie or a photo saved to your camera roll and alter it using neural-network technology. FaceApp is capable of adding two different kinds of smiles to your photo, aging you or making you look younger, or swapping your gender. There's also a filter called "Flash," which seems to lighten and smooth skin.

The app isn't perfect by any means. It often added strange colors to people's skin when making them look younger, and changing a woman's face into a man's often yielded some truly horrifying results.

We decided to test it out on various tech CEOs and celebrities. Here's what it looks like.