Abstract: A low-cost, magnetically-driven device that enables visualization and quantification of dynamic changes in cell behavior during mechanical stretch. Using this device, it was observed that nuclei of mouse embryonic skin fibroblasts underwent rapid but divergent responses to strain magnitude, showing nuclear area increase and chromatin decompaction during 5% (low) strain, but nuclear area decrease and chromatin condensation during 20% (high) strain. Only responses to low strain were dependent on calcium, while actin inhibition abrogated any nuclear response and increased stretch-induced DNA damage. Stretch-activation revealed a shift in actin filaments away from (low strain) or towards (high strain) the nuclear periphery. The findings suggest that different pathways control strain level-dependent cell behavior and that mechanical confinement of nuclei through actin may be a protective mechanism during high strain loads.