Adsorbed layer thickness (t) of several dilute polymeric systems were measured by ellipsometry. For physically adsorbed homopolymers, t scales as M0.5 and M0.4 in theta and good solvents, respectively. Conformational change from “mushroom” to “brush” were observed for a terminally attached polyelectrolyte by adjusting electrostatic “excluded volume”. By applying potential for polyelectrolytes adsorbed on a metal surface, both stretched and squeezed conformations were realized. Stiff polymers can be adsorbed either end on or lying flat configurations. Intercalation adsorption into clay lamellas, i.e. slits resulted disk-like conformation. Thus, the concept of “conformation control of adsorbed polymers” was experimentally realized.