The viscosity of a fluid and the diffusion coefficients of its constituents can provide important points of reference for the understanding of a large variety of transport-related phenomena in a plethora of systems. The viscosity of a solvent largely determines the translatoric mobility and rotational dynamics of solutes, such as small-sized drug molecules, or macromolecules, like proteins and DNA fragments. The diffusion coefficients often control how long molecular aggregates such as ion pairs and hydrogen bonded entities stay in close proximity. The diffusion of ions in an electrolyte system in combination with their concentration largely determines the electrical conductivity. Diffusion as a mechanism is at the root of describing mass transfer processes, while the viscosity characterizes the overall fluidity of the embedding matrix.