This chapter examines some dynamic properties of polymers in dilute solution, with a particular emphasis on the viscosity. The column is packed with porous particles with some characteristic range of pore sizes, which should correspond roughly to the typical sizes of the polymers to be analyzed. The packing material can be made from a variety of substances, but the chosen substance must be compatible with the solvent, polymer, and temperature to be employed. For example, Styragel columns are made from styrene/divinylbenzene copolymers, in the form of cross-linked beads. Such columns are suitable for relatively nonpolar polymers that dissolve in good solvents for polystyrene such as toluene, THF, or chloroform. In many experiments to study polymer diffusion, some fixed, small amount of the polymer is placed in contact with the medium into which it will diffuse.