Starting with Einstein's work on Brownian motion, mobility of colloidal particles is viewed as produced by random bombardment by surrounding molecules. Thermal fluctuations in liquids cannot be viewed as single-particle collisions since they occur as collective excitations. A view of Brownian diffusion as caused by fluctuating collective forces imbalanced at different sides of a tagged particle is a more accurate representation. This talk discusses diffusivity of small molecular solutes and proteins as caused by fleetingly shifting balance between van der Waals and electrostatic forces. They turn out to be surprisingly correlated for a diffusing protein. The famous violation of the Stokes-Einstein-Debye relation turns out to arise from the shifting balance between electrostatic and van der Waals forces affecting rotational and translational diffusion.