T cells experience different mechanical signals in different tissues. Researchers have engineered a tissue-mimicking hydrogel model to show that more elastic tissues induce T cells to become effector-like T cells with strong tumor-killing potential, while more viscous tissues induce them to become memory-like T cells. This new concept could help advance adaptive T cell therapies by producing desired patient-specific T cell populations in the dish that could provide stronger effects when infused back into the same patient.