We’re a curious lot. Always looking for new stuff to do. Always looking for new places to go. Maybe that’s why we feel it’s our destiny to travel to other planets. And not just to drop in, dig around, grab some rocks and catch a ride home on the next feasible trajectory, but to settle in, maybe even build a colony. Doing that will almost certainly require growing plants in space. Plants are the only option we have for food, beyond what we take with us. They’re also natural water purifiers, oxygen generators and carbon dioxide scrubbers. In short, little life-support machines.