The smallest size of eddy that can be formed in a fluid. The size of an eddy is dependent on the viscosity of the fluid. In a stirred vessel, the Kolmogorov eddy size also decreases with increasing stirrer speed. Large-sized eddies are unstable and eventually break up to form smaller eddies with the kinetic energy of the initial large eddies being dissipated into the smaller eddies stemming from it. These smaller eddies undergo the same process, giving rise to even smaller eddies. Thus the energy is dissipated to the point that the viscosity of the fluid can effectively dissipate the kinetic energy into internal energy. The theory was first proposed in 1941 by Russian mathematician Andrey Nikolaevich Kolmogorov (1903–87).