Chromogenic materials allow the transmittance of visible light and solar energy to be varied under the action of an external stimulus This paper first discusses buildings related energy savings that can be accomplished by chromogenic technologies, and their beneficial effects on comfort issues We then summarize recent work on thermochromic VO(2)-based thin films with particular attention to multi-layers of VO(2) and TiO(2) and to new VO(2) Mg films for which the doping gives significantly lowered absorption of visible light The final part covers electrochromic materials and devices with foci on coloration efficiency and on durability issues for foil-type constructions based on films of WO(3) and NiO. (C) 2009 Elsevier B.V All rights reserved.