There are seven basic preschool concepts: Observing, Comparing, Classifying, Measuring, Communicating, Inferring, Predicting. I think the most important concept is the ability to observe. Once a child is able to make observations of the natural world around them each of the other concepts falls into place as they test the question they have. Even when trying to do higher-level science, the first thing that starts off the science experiment is " What... If..."