Percolation and critical points

The interplay between critical percolating clusters and critical points in physical systems and models is reviewed. The main emphasis is given to syst ems such as colloids and gels. Much information on the main mechanism leadi ng to percolation in correlated systems can be obtained from the study of t he Ising model. It is emphasized that different cluster definitions are nec essary for studying different phenomena and that the possibility of experim entally detecting the percolation line is related to the cluster lifetime. Some results on the interplay between critical points and percolating clust ers in fluids are also discussed.