The migration of Millennials to urban downtowns is one of the most discussed trends of the 2010s. Downtowns are changing in response to Millennials, but we know less about how or why these changes are occurring. This report helps to fill this gap by exploring how real estate developers are cementing Millennials in the downtowns of two Sunbelt cities, Phoenix and Houston, which are emerging sites of Millennial migration. We draw findings using data from the U.S. Census, regional media, and interviews with 22 experts involved in Phoenix and Houston’s downtown housing markets. Downtown developers perceive Millennials as needing housing that is authentic, flexible, and socially conscious and provides an inside/out, constantly connected life. These developers have molded their perceptions of Millennials’ lifestyle preferences into the brick and mortar of downtown Phoenix and Houston through innovative building design and site selection. The symbiotic actions of Millennials and developers in downtown Phoenix and Houston also are reshaping these regions’ housing markets. Underlying concerns including rising housing costs and gentrification in the downtowns and reduced demand for housing in the suburbs, if Millennials living downtown stay.