The Multiscale Experimental Ecosystem Research Center has conducted a series of mesocosm experiments to quantify the effects of scale-in terms of time, depth, radius, exchange rate, and ecological complexity-on biogeochemical processes and trophic dynamics in a variety of coastal habitats. The results indicate that scale effects can be categorized as (a) fundamental effects, which are evident in both natural and experimental ecosystems, and (b) artifacts of enclosure, which arc solely attributable to the artificial environment in mesocosms. We conclude that multiscale experiments increase researchers' understanding of scale in nature and improve their ability to design scale-sensitive experiments, the results of which can be systematically compared with each other and extrapolated to nature.