The use of microcosms in marine research is a recent development, beginning in earnest in the early 1960s. A major recent trend is the use of microcosms as living models of specific natural ecosystems or types of systems, in contrast to earlier research that tended to use microcosms as small-scale environments. Microcosms have always been used in research dealing with species succession, predator-prey interactions, etc., and much recent work has emphasized their use to explore the biogeochemical cycling of various materials, especially pollutants, and the effects of these materials on the biology and chemistry of marine ecosystems.