The impact of the experimental separation of the coherent and incoherent co
ntribution to scattering is outlined through three case studies of increasi
ng complexity. They range from studies of liquid sodium through lattice gas
of deuterium in a single crystal of niobium to polymers and their blends.
In these cases, polarization analysis affords distinction between dynamic o
rder and disorder in a liquid, differentiation between the tracer and chemi
cal diffusion, and a confirmation of the existence of a short-range order i
n amorphous polymers, respectively. In addition to an outline of the state-
of-artin this field, future trends are speculated upon. (C) 1999 Published
by Elsevier Science B.V. All rights reserved.