Humans don't naturally blend in with much, and aside from blushing, we can't change colors like chameleons or cuttlefish. But we do use one kind of camo few other species have: clothes. We've made DIY disguises for centuries, often borrowing ideas from nature to help us hunt food and fight wars.
Man-made camo has found lots of other uses over the years, too, such as scientists dressing up as whooping cranes or nude models being painted like tigers, not to mention all the disguises people make every Halloween. And now even the ultimate form of camo is within sight: Scientists at the University of St. Andrews reported in 2010 that they're developing an invisibility cloak.