Femto photography (femto means trillionth) lets you create slow motion videos of light in motion. That means that we can actually see how light moves around. We can see inside people without an Xray because some light bounces around inside you. We can see around the corner by looking at how light bounces off things around corners (or build medical technology or make a way for disaster responders to find people inside burning buildings). We can make art. Also, because we're recording at close to the speed of light, we get relativistic effects.