Quantifying forces in cell biology

Physical forces influence the growth and development of all organisms. In the second Review in the Series on Mechanobiology, Trepat and co-authors describe techniques to measure forces generated by cells, and discuss their use and limitations. Cells exert, sense, and respond to physical forces through an astounding diversity of mechanisms. Here we review recently developed tools to quantify the forces generated by cells. We first review technologies based on sensors of known or assumed mechanical properties, and discuss their applicability and limitations. We then proceed to draw an analogy between these human-made sensors and force sensing in the cell. As mechanics is increasingly revealed to play a fundamental role in cell function we envisage that tools to quantify physical forces may soon become widely applied in life-sciences laboratories.