Ferroelectric liquid crystals (FLCs) have been under investigation for use in electro-optic devices for over a decade. In this review the development of the studies of the optics of FLCs over this period is discussed. Starting from the first electro-optic switching studies undertaken in 1980 by Noel Clark and Sven Lagerwall, and the structure in a FLC cell proposed to explain the effects, the process of developing understanding is followed. The review concentrates on the structure revealed to be present in a FLC filled cell, as this is of central importance in the development of optical devices using this material. Problems encountered in device development, and the approaches taken to overcome them are discussed, including special surface alignments, AC stabilization, and treatment of cells with large electric fields. FLC continuum theory is also discussed as this is needed for calculation of the liquid crystal director profiles, and hence the determination of optical performance. More recent developments in anti-ferroelectric liquid crystals and novel switching mechanisms are considered. An appendix outlines the 4 × 4 matrix approach to device optics calculations.