The simple answer to this question is that it depends on your needs. For elementary and middle school teachers, though, the author has found that a high percentage of teachers lack the proper background in science content to teach effectively. There are many different kinds of professional development (PD) opportunities with respect to science content. In this article, the author will address a couple of those that relate to science content and, along the way, provide his thoughts on the science content that is likely to help you the most.