The brain generates a tremendous variety of behaviors, but how it achieves these feats remains largely unknown. Genetics and molecular tools yield fundamental insights into how the brain senses its environment and determines an appropriate course of action. This course will describe modern genetic manipulations (eg, CRISPR editing) and neuronal interventions (e. g., optogenetics), and discuss the quantification of behavioral outputs. Course consists of lectures plus readings and group discussions of primary scientific literature.