Epilepsy is a common neurological disorder and a major source of disability, with a third of all epilepsies unresponsive to existing treatments. To develop new and effective treatments, it is critical to identify seizure control points in the brain – regions, cells and circuits. We recently developed an approach to deliver light to the brain to control the activity of specific cell types, which specifically blocked seizures without affecting normal brain activities. In this proposal, we will develop novel optogenetic tools to determine causal links between the activity of specific cell types and various seizure types in behaving rodents.