Clay minerals are natural materials well known for their role in retention and persistence of organic and inorganic compounds in soil. Clay minerals are being modified through different processes to alter their charge and surface properties tailored for specific purposes. Modified clays in general include pillared layered clays, organoclays, nanocomposites, acid and salt-induced and thermally and mechanically induced modified clays. Pillared organoclays and nanocomposites constitute a novel class of materials, mainly one kind of modification of expanding 2 : 1 clay minerals.