As our technology advanced, so has the sophistication of our classification systems. Over time, we’ve moved from the ancient Greeks’ four elements to the periodic table, and from classifying animals by the way they move to comparisons of their DNA sequences. Classification systems are an essential tool in all branches of science, but also help bring order to our everyday lives in the form of phone directories, library catalogs, bus schedules, supermarket aisles, and countless other ways. This issue of Science Scope has some interesting classification activities to build on the observation and classification basics that students bring with them from elementary school.