What is the app do make your picture 3 into 1?

So whenever i'm on instagram I see people getting like 70 likes on their photo because they edit their photo & put flames or lines across the picture ' so what app do I use to put my picture into 3's basically like a collage but not 4's into 3's going across sideways for the Iphone or Android I have both it doesn't matter

PhotoGrid

For iPhone, you can try Collage Pro

For pc or mac, you can try Softease CollageFactory Express.
http://www.softease.biz/collagefactory-express.html