The National Science Education Standards outline what students need to know, understand, and be able to do in science at different grade levels. The Science Explorer program reflects a number of changes in emphasis in science education that are embodied in the National Science Education Standards. In the current standards, emphasis has shifted from knowing scientific facts to understanding scientific concepts. Rather than separating science knowledge and science content, the standards require an integration of all aspects of science content, the approach taken by the Science Explorer program. This correlation is for each unit in the Science Explorer.