On April 9, the Treasury Department debuted the first details of a new and far-reaching community-based tax incentive. In 18 states, newly designated zones could see a wave of new investment under a little-known provision of the recent tax overhaul. These opportunity zones are designed to lure investment to the nation's poorest urban, suburban, and rural communities with a powerful tax incentive. By the accounts of some experts, the program could deliver a vital injection to areas that haven't yet recovered from the Great Recession. Yet it could also fuel gentrification in those communities where too much opportunity, too fast, has led to rapid displacement.