There is increasing evidence that multicellular structures respond to mechanical cues, such as the confinement and compression exerted by the surrounding environment. In order to understand the response of tissues to stress, we investigate the effect of an isotropic stress on different biological systems. The stress is generated using the osmotic pressure induced by a biocompatible polymer. We compare the response of multicellular spheroids, individual cells and matrigel to the same osmotic perturbation. Our findings indicate that the osmotic pressure occasioned by polymers acts on these systems like an isotropic mechanical stress. When submitted to this pressure, the volume of multicellular spheroids decreases much more than one could expect from the behavior of individual cells.