Some laboratories are too serious—and too dangerous—to be any fun for lay visitors. Biosphere 2, though, conducts its earth-systems research missions in a human-friendly, glass-enclosed microcosm that wows visitors with drastically changing temperatures, lush plant life, and tales from two human-lockdown experiments (1991-94). From Phoenix: I-10 east, Hwy. 387 east, Hwy. 79 southeast, Hwy. 77 northeast.