When multiple cells assemble to build an animal, they have to start by breaking away from their uniformity. It is quite common for cellular systems to achieve this symmetry breaking through self-organization, i.e. exclusively due to interactions and properties of the cells rather than pre-existing patterns or blueprints. Hydra, a freshwater polyp, offers an unrivaled example of such a system. These are simple tube-like animals organized along a single axis, at one end of which is the mouth surrounded by tentacles and at the other the foot with which they attach to solid substrates. They can be dissociated into single cells, and these cells are able to regenerate a full animal when aggregated. To accomplish this, they first have to establish a special group of cells acting as an organizer. Although this process has been under intense investigation, how Hydra cells self-organize remains a mystery.  Newer studies implicate mechanical stimuli and we are trying to understand the interplay between mechanics and biochemistry on this cellular system. Our results point to a critical role of tissue stretching that parallels events in evolutionary younger species.