Many cells are capable of responding to mechanical stimuli in their environment, such as fluid flow, compression, pressure and stretch. By means of mechanosensors, cells may detect and respond rapidly to stimuli (e.g. touch, sound waves, limb position) or they may begin a structural response to chronic events. For example, in limbs that are constantly exercised, cells will produce bigger muscles, stronger ligaments and denser bone. This may involve the recruitment, proliferation, differentiation and stimulation of a variety of cells. Investigations are aimed at discovering the cell components responsible for these responses and understanding the process that links receptors to signal transduction to the cell response. This chapter discusses each of these areas.