In 1979, having just completed a degree in fine arts as a painter, Greenberger took a job as activities director at a nursing home in Boston. On his first day, he met the residents of the nursing home and abandoned painting in favor of conversation. "This is my art," he said. In this unexpected setting, Greenberger found an unusual medium and a desire to portray the people he met as living human beings instead of "just repositories of their memories or the wisdom of the ages." Instead of collecting oral history about significant events, Greenberger focused on talking one-on-one with ordinary people about ordinary things—the joy of a close shave or answers to "Can you fight city hall?".
Greenberger began publishing his conversations with old people in The Duplex Planet, a small, homemade magazine he started in 1979, and still publishes today. It has subsequently found larger audiences in other forms, which are all derived from the original template. A series of personal commentaries drawn from Greenberger's experiences with this body of work has aired regularly on National Public Radio's "All Things Considered". Greenberger was the subject of a segment in 2007's "Life Part 2: Language of Aging", part of a PBS series on aging.