(Frank) Percy Smith was born on 12 January 1880 at 15 Elizabeth Terrace, Islington, the son of Francis David Smith, a printer, and his wife, Ada Blaker. In childhood he became fascinated with animal and plant life. To please his family, however, at the age of sixteen he became a clerk with the Board of Education. The work was hatefully tedious to him, but it did allow him time to pursue his hobby with ever greater attention. He turned naturally to photographing his subjects, and it was a photograph of a bluebottle's tongue that attracted the attention of film producer Charles Urban. Urban aimed to bring documentary and educational film subjects to the general public, and encouraged Smith to repeat some of the close-up studies he had made on film. On 3 June 1907 Smith married Kate Louise (b. 1880/81), daughter of James Ustonson, an optician. Smith's wife was the only assistant he would allow when working. There were no children.

Smith's initial experiments were followed up by more professional work conducted at home, which Urban started to exhibit in London theatres. Scenes of a fly performing such feats as juggling a cork, in The Balancing Bluebottle, astonished and delighted the public, and aroused considerable newspaper interest. Having gained no response from the Board of Education to his proposals for using film as an educational medium, Smith joined Urban as a full-time film-maker in 1910. He set up his self-made apparatus in his Southgate home and began to specialize in the filming of accelerated plant growth, using stop-motion photography, using the hour-wheel of a clock to trigger an electrical circuit to expose a single frame of film, and raising the camera by degrees as the plant subject grew. Such work was always preceded by meticulous research to determine the growth rate, and some films could be a year in preparation before a single frame was exposed.

The first of the plant films, The Birth of a Flower, was issued in the Kinemacolor colour film process in 1911. Smith made over fifty nature films for the Urban Science series shown at the Scala Theatre, including several employing microscopy, before the outbreak of the First World War, when he first turned to the production of novel animated war maps. Smith then joined the navy, where he was made a sergeant of kinematography and photographed aeronautical and balloon experiments, as well as the surrender of the German fleet at Scapa Flow. After the war, with Urban now in America, Smith was lucky to find another imaginative producer in H. Bruce Woolfe of British Instructional Films. Smith began work on Woolfe's Secrets of Nature in 1922, an enduringly famous series of short documentaries that were popular in cinemas and festivals throughout the 1920s and 1930s, and were for a long time acclaimed as the very best of British film production. Their simple yet meticulous observation engrossed all who saw them, and they became a mainstay of the non-theatrical educational film circuit for many years. He was especially involved in underwater photography and micro-cinematography. Smith wrote The Secrets of Nature (1939) and other guides to the subjects of his scientific films with educationist and film-maker Mary Field, a long-time associate.

Percy Smith was an exceedingly private man. His work was initially viewed with some scepticism by the scientific community, which simply doubted the evidence of Smith's films, for they not infrequently overturned long-held assumptions about animal activity. But his methods were impeccable, and from the 1920s onwards his work was widely recognized for its originality and rigour, and he collaborated with such eminent scientists as biologist Dr Julian Huxley and botanist Dr E. J. Salisbury. He died on 24 March 1945 at 107 Chase Road, Southgate, after gassing himself. The coroner's certificate recorded that Smith killed himself while the balance of his mind was disturbed.