He began photojournalism in 1989, when his image ("Kisses to All, Berlin Wall") of a tutu-clad girl with a champagne bottle became a symbol of the fall of the Berlin Wall. While working for the Paris-based photo agency Agence Vu in October 1993, Greene was trapped and almost killed in the White House in Moscow during a stand-off between President Boris Yeltsin and the parliament. He covered the war-torn countries Azerbaijan, Bosnia and Herzegovina, Georgia, Iraq, Somalia, Croatia, Kashmir, and Lebanon. He took pictures of the genocide in Rwanda in 1994 and the US Gulf Coast in the aftermath of Hurricane Katrina in 2005.