How does the brain translate sensory stimuli into a behavior? In his first iBiology talk, Dr. Florian Engert explains that larval zebrafish are an excellent model to tackle this question. Larval zebrafish are tiny, translucent, and genetically tractable vertebrates.  By making transgenic fish with labelled neurons, it is possible to visualize neuronal activity in the entire brain of a living and awake fish.  Engert introduces the virtual behavior simulators that his lab members use to trigger and measure neuronal activity in the fish.