Although his original goal was to display and study the stresses on moving machine parts otherwise invisible to the naked eye, Edgerton later used very short flashes of light as a means of producing dramatic still photographs of fast-moving objects in transit, such as bullets in flight, hovering hummingbirds, and falling milk drops splashing into a bowl. His camera had no shutter. The film was pulled through continuously as in motion picture cameras --- but at much higher speeds --- and exposed by a stroboscopic flash lasting 1/1,000,000 of a second or less.