As children grow and mature, the scope of their environment predictably expands from the womb to the wider community to the broadest reach of the planet. The child’s built environment is a central factor in this progression. Both known and newly emerging diseases are linked to risk factors within the built environment, including injuries, lead poisoning, and the current epidemics of asthma and obesity. Building and land-use policies can either undermine or promote safety, health and optimal development while simultaneously preserving future resources. This newly evolving field is ripe for future research. We urgently need pediatric.