This is the eighth in the aperiodic series of ellipsometry conferences, and the third devoted specifically to spectroscopic ellipsometry. I discuss the evolution of the field mainly from a technological perspective, and the changes that must be made in analytic procedures as accuracy requirements are increased from 1 to 0.1%. The current interest in Mueller-matrix spectroscopy motivates a discussion on how to include depolarization artifacts in Mueller-matrix calculations from first principles. Representative applications include extensions to the far infrared and vacuum ultraviolet, the determination of all elements of the Mueller matrix with a stationary sample, and the determination of critical dimensions by scatterometry. (C) 2003 Elsevier B.V. All rights reserved.