Life is the most complex phenomenon in the universe. Yet, remarkably, many of its most complex attributes scale with size in a surprisingly simple fashion. As we look at organisms from the tiniest to the largest, lifespans and growth rates, for example, increase with exponents which are typically simple powers of 1/4. Geoffrey West, president of the Sante Fe Institute, shows how these scaling laws follow from fundamental generic principles embedded in the dynamical and geometrical structure of underlying networks, leading to a general quantitative theory that captures essential features of many diverse biological systems. He then extends these ideas to discuss urban systems: to what extent are cities an extension of biology?