The study investigates whether stem cells can remember past physical signals and how these memories can be exploited for mechanical dosing. Human mesenchymal stem cells (hMSCs) cultured on soft poly(ethylene glycol) (PEG) hydrogels showed that activation of the Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding domain (TAZ), as well as the pre-osteogenic transcription factor RUNX2, depended on prior culture time on stiff tissue culture polystyrene (TCPS). Mechanical dosing of hMSCs on initially stiff and then soft phototunable PEG hydrogels resulted in either reversible or irreversible activation of YAP/TAZ and RUNX2, depending on the duration of mechanical dosing. Increased mechanical dosing on supraphysiologically stiff TCPS biased hMSCs toward osteogenic differentiation. The findings suggest that stem cells possess mechanical memory, with YAP/TAZ acting as an intracellular mechanical rheostat that stores information from past physical environments and influences cell fate. The study also demonstrates that mechanical dosing can irreversibly influence stem cell fate, highlighting the importance of considering mechanical dosing in stem cell culture and expansion.The study investigates whether stem cells can remember past physical signals and how these memories can be exploited for mechanical dosing. Human mesenchymal stem cells (hMSCs) cultured on soft poly(ethylene glycol) (PEG) hydrogels showed that activation of the Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding domain (TAZ), as well as the pre-osteogenic transcription factor RUNX2, depended on prior culture time on stiff tissue culture polystyrene (TCPS). Mechanical dosing of hMSCs on initially stiff and then soft phototunable PEG hydrogels resulted in either reversible or irreversible activation of YAP/TAZ and RUNX2, depending on the duration of mechanical dosing. Increased mechanical dosing on supraphysiologically stiff TCPS biased hMSCs toward osteogenic differentiation. The findings suggest that stem cells possess mechanical memory, with YAP/TAZ acting as an intracellular mechanical rheostat that stores information from past physical environments and influences cell fate. The study also demonstrates that mechanical dosing can irreversibly influence stem cell fate, highlighting the importance of considering mechanical dosing in stem cell culture and expansion.