In 1857, Rudolf Clausius shows that one can understand the heat that a body generates as the rapid motions of its invisible atoms or molecules.
Microscopically small bodies suspended in liquid also exhibit random vibrating movements, which is called Brownian motion.
It is fair to assume that this vibrating motion is caused by the bodies colliding with the liquid\u2019s atoms or molecules.
Experiments to explain Brownian motion with the kinetic theory of heat, however, produce problematic results.