In this presentation I will talk about an interesting physical experiment: time reversal of waves. In time reversal, wave signal from a source is recorded, time reversed and sent back. The back propagated wave will refocus on the source. This phenomenon has many potential applications in non-destructive testing, imaging and secure communications. In this talk I will discuss auto-focusing property of time reversal and super-resolution in random medium. Applications in target detection and imaging will be demonstrated.