To answer the seemingly simple question “Have I been here before?” we must use our memories of previous experiences to determine if our current location is familiar or novel. Scientists have now identified a region of the hippocampus, called CA2, which is sensitive to even small changes in a familiar context. The results provide the first clue to the contributions of CA2 to memory and may help shed light on why this area is often found to be abnormal in the schizophrenic brain.