Content is a vital component of what we personally need to know and understand if we are to teach children to know and understand. But understanding how students learn, acquiring strategies to assure that will happen, and then knowing if they understand are all equally important. Teachers have a lot of knowledge. They also need to know how to apply it. But if teachers don’t see the value of the professional development (PD) in which they are involved, they will not be engaged. In this article, the author discusses why “one size doesn’t fit all" when it comes to PD.