In 2010, cancer biologist Lei Cao—inspired by a family member who had died of cancer—wondered whether she could combat it by looking beyond drugs or genes. Her team at OSU created a 1-square-meter enclosure filled with so many mazes, running wheels, and bright red, blue, and orange igloos that her daughter dubbed it “Disneyland for Mice.” <img class="fragment-image" src="https://d2ufo47lrtsv5s.cloudfront.net/content/sci/359/6376/624/F3.medium.gif"/> A fish at the University of Michigan in Ann Arbor gets to choose between an empty tank and one filled with marbles. PHOTO: AUSTIN THOMASON/MICHIGAN PHOTOGRAPHY When injected with cancer cells, animals housed there developed tumors 80% smaller than those in control mice, or no tumors at all. Cao even discovered a possible mechanism: A stimulating environment seemed to activate the brain's hypothalamus, which regulates hormones that affect everything from mood to cancer proliferation. “We showed that there's a hard science behind enrichment,” she says. “You can't just treat the body—you have to treat the mind.” - science.sciencemag.org