Evolution is a fundamental principle in biology, yet students, teachers, and the public at large all too often misunderstand the way it works. I introduce a hands-on exercise that emphasizes tree-thinking and phylogenies to organize biodiversity. During the activity, students observe and investigate the patterns and processes of macroevolution by first building unique specimens through gradual, stepwise changes in characters. They then switch specimens with another group and, by observing shared characters, hypothesize the evolutionary relationships of the specimens by drawing phylogenies. The exercise has been used for several years, and pretest—posttest results confirm that it significantly improves student understanding of macroevolution and phylogenetics.