Habits are a major part of everyday life, allowing us to automate many routine behaviors. The same brain mechanisms underlying habits might also contribute to unhealthy compulsive behaviors. If we can understand how habits work in the brain, then we may be able to promote good habits while suppressing the bad. My goal for the Grass Fellowship is to locate the memory trace for a habit by harnessing the power of activity-dependent gene regulation. Ultimately, I hope to demonstrate that a subset of corticostriatal projections is necessary and sufficient to store and express a habit memory.