The Second Winter School on the " hysics of Finely Divided Matter" was
held at the Centre de Physique des Houches from 25 March to 5 April
1985. This meeting brought together experts from the areas of gels and
porous media. People with different backgrounds - chemists, physicists -
from university as well as industrial labora- tories, had the
opportunity to compare their most recent experimental and theoreti- cal
results. Although the experimental situations and techniques may seem at
first sight unrelated, the theoretical interpretations are very similar
and may be divided roughly into two categories: percolation and
aggregation. These are present for the description of the synthesis of
some gels as well as for a description of the struc- ture of packings.
They are also a precious help for understanding flows in porous media
and hydrodynamic instabilities such as viscous fingering. A different
aspect, still in its early stages, deals with the influence of a ran-
dom medium on a phase transition. This leads to metastable states and is
interpreted in terms of random fields. The following topics were
covered: introduction to physical and chemical gels structure of
packings and porous media microemulsions percol ati on aggregation
elastic and dielectric properties of ill-connected media properties of
gels near and far from the gelation threshold flow, diffusion and
dispersion in porous media transitions in porous media. Most of these
are rapidly growing subjects, and we hope that these proceedings will
serve as a reference for those entering this fascinating area.