The cerebellum is a fascinating brain area to research. It contains most of the brain’s neurons, is composed of a highly structured and stereotypical arrangement of cells, has a similar cortical area as the cerebrum, is highly interconnected with the forebrain and brainstem, and has expanded in size over the course of evolution to sustain increased mental and physical capacity. For over 100 years, specific dysfunction in or damage to the cerebellum has been known to cause dramatic deficits in motor coordination. Now, with novel behavioral assessment and advanced technological tools, including computational modeling, functional neuroimaging, advanced tract tracing methods, neuromodulatory tools, and the ability to directly modify gene expression, mounting evidence has dramatically broadened the fields perspective of the cerebellum’s role in healthy behavior, implicating it in regulating cognition, mood, reward, decision making, pain, and addiction.