5S Why's is an iterative interrogative technique used to explore the cause-and-effect relationships underlying a particular problem. It is most effective when the answers come from people who have hands-on experience of the process or problem in question. The method is remarkably simple: when a problem occurs, you drill down to its root cause by asking "Why?" five times. This 5S Why's overlay is quick and easy and can be place on any existing whiteboards.