After serving as photo assignment editor for the Associated Press in New York, Greenberg co-founded the New York-based Visions Photo Agency and is now director of development for the photo agency World Picture News. He has won World Press Photo awards. His books include "Art of the Massai," "Voyager" and "Amazon Diary – The Jungle Adventures of Alex Winters." Greenberg was a senior digital advisor to "A Day in the Life of Africa."