The conversion of a physical force into a biological response. Prime examples are the responses of mechanoreceptors to stimuli such as touch, sound, and stretching of muscles. The physical forces open or close ion channels in the sensory cell, which alters the cell’s membrane potential and triggers the release of neurotransmitter and/or the generation of electrical signals in the form of action potentials. However, the mechanical interactions between individual cells, and between cells and their external environment, affect many aspects of a cell’s life, including differentiation, tissue organization and integrity, cell motility, and even tumour formation. The cytoskeleton, responsible for maintaining the cell’s internal structure, is a key component in relaying external forces to the cell’s interior. Mechanotransduction is also involved in the colonization of host cells by infecting bacteria.