Cells constantly change their molecular state in response to internal and external cues1. Mapping cellular activity in tissues with spatiotemporal precision is essential for understanding organ physiology, pathology, and regenerative processes. Current cell-sensing modalities primarily rely on either endpoint analysis that takes static snapshots, or real-time sensing that monitors a small subset of cells3,4. Here, we introduce Granularly Expanding Memory for Intracellular Narrative Integration (GEMINI), an in cellulo recording platform that leverages a computationally designed protein assembly as an intracellular memory device to record the history of individual cells. GEMINI grows predictably within live cells, capturing cellular events as tree-ring-like fluorescent patterns for imaging-based retrospective readout. Absolute chronological information of activity histories is attainable with hour-level accuracy.…