Almost all biological processes are involved in the modulation of mechanical force whose functions are physically involved with cytoskeleton. This unique form of mechanical force is called structural mechanics and it is regulated realtime by a variety of factors, such as exogenous force, motor proteins, osmotic pressure, mechanosensitive ion channels (MSCs), intracellular mechanosensors and actin assembling. FRET-based force sensors which can be incorporated into structural proteins and turn structural force into optical signal can provide a realtime measurement of force in live cells. With the advent of the space age, structural dynamics will play a more and more important role in life and medical research.