Scientific and medical illustration is often characterized by a twofold need: for accuracy and for clarity in presenting information. It would be more appropriate, however, to say that such illustration is utilized in assisting the reader in "seeing" information within the context of a particular theory or scientific reality. Some images present theory based on careful study. Other images are based on observed, though selective, reality. A third type of image shows the way to conduct an experiment or procedure, or simply the equipment needed. The developments in book illustration techniques shown on this website should be viewed with an eye to economic factors which have always been a major component of book production.

All book illustration processes can be divided into four basic groups: relief printing, chiefly woodcut and wood engraving; intaglio printing, including engraving, etching, and mezzotint; planographic printing, chiefly lithography and chromolithography; and photography. In the 1960s, when the text as well as the illustrations began to be reproduced photographically, offset lithography, a photolithographic printing process, took over commercial book production and held the field until today's digital revolution.