Let's get one thing clear: It's all about the bum. Sure, built biceps fill out a shirt and six-pack abs are the prize of every beachgoer, but the back is where it's at. A bodacious booty is essential to a good physique and not just for stage-bound fitness contestants. Everyone seems to want a great bum. Photos of posteriors flood the Internet and are often the most viewed and "liked" body part on social media. There's just something magical about a beautiful butt!