The Biosphere 2 project, a 1.2 hectare materially-closed mini-biosphere that supported teams of biospherian crews from 1991-1994 provides a host of ecological and human-biosphere lessons relevant to our global biospheric challenges. Because of its high visibility through worldwide media coverage, the project advanced public understanding of what a biosphere is and the roles that humans can constructively play in keeping ecosystems and atmosphere healthy. The present paper reviews the fairly recent scientific understanding of our global biosphere and some of the intriguing results from Biosphere 2. It also examines some of the reasons that Biosphere 2 aroused controversy because of narrow definitions and expectations of how science is to be conducted. The cooperation between engineers and ecologists and the requirement to design a technosphere for Biosphere 2 that supported the life inside without harming it has enormous relevance to what is required in our global home. There was an unexpected and profound connection that the ‘biospherian’ crew inside Biosphere 2 felt to their living biosphere. Biosphere 2 also demonstrated new kinds of roles that can be played by people aware of a biosphere as their life support system.