It is characterized by the zigzag motion of suspended colloidal particles, occurring due to the bombardment of one particle or molecule by others. This type of movement of particles was first of all observed by Robert Brown in 1827 in the colloidal solution and hence such movements are known as Brownian movements.
The higher the temperature, more rapid the movement and – thus viscosity of cell is decreased. This means that high viscosity indicates a more gel-like state of protoplasm and low viscosity, a more sol-like condition