Medicine had always been a subject where textual descriptions were insufficient as an aid to diagnosis and understanding and since the Renaissance artists had used their skills to illustrate the complex melding of flesh and bone. Photography was immediately accepted as a tool that could provide accurate renditions of the subject at hand.
 
Dr Guillaume-Amant Duchenne de Boulogne (1806-1875) was assisted by the photographer Adrien Tournachon (1825-1903) in photographing the results of his neurophysiological studies of the face. Dr Duchenne applied electrical shocks to different facial muscles to study their relationships in the formation of expressions. The results were published in his 1862 work Mécanisme de la physionomie humaine, ou analyse électrophysiologique des passions which is one of the earliest medical works accompanied by photographic illustrations. The Revue Photographique des Hopitaux de Paris of 1869 was edited by Dr. A. de Montmeja, a Parisian ophthalmologist and pioneering medical photographer, and it was the first medical journal to contain photographs.
 
Oscar Gustave Rejlander (1813-1875) is best known for his portraits but he also assisted Charles Darwin (1809-1882), the evolutionary biologist, in creating about twenty photographic studies of facial expressions that were published in The Expression of Emotion in Man and Animals (London, 1872).
 

• Lennart Nilsson (1922-): whose book 'A Child is Born' used extraordinary photography to show the process in ways never dreamt of.