Throughout the natural world and our human-designed world, design and evolution seem to go hand-in-hand. Some of the most astonishing and complex designs known to humankind—the embryogeny process, the immune system, the brain, the very structure of DNA—are products of natural evolution, not human endeavor. In addition, the progress of our own designs seems evolutionary, as the best concepts from existing designs are combined with some small variation to produce the next generation of cars, computers, and indeed, most types of human design. And now, as the papers in this and subsequent special issues will show, our computers are allowing us to harness the power of evolution directly, to aid the design process.