“Turning 40” may bring to mind a catalogue of cliches, but for Molly Riordan (PhD ’29), the milestone brought something very different. Instead of a midlife crisis, she said yes to a PhD program. The story began years earlier, in 2008, on a Brooklyn rooftop overlooking the Manhattan skyline. Riordan was standing inside one of New York City’s first rooftop farms, surrounded by crops of tomatoes, peas, and peppers. It brought to mind the farmland she had passed while driving across New York State, sparking a powerful question: Where does the rest of our food come from?