A new study shows that precisely manipulating brain activity during sleep can help mice retain memories that would normally fade, offering a potential pathway for treating memory loss conditions. Researchers identified a specific sleep-related pattern—large sharp-wave ripples—that signals when new experiences are being transferred from the hippocampus to the neocortex for long-term storage. By boosting these ripples at just the right moment using optogenetics, scientists enabled mice to remember brief encounters they would typically forget.