The measurement of appearance of objects seen by individuals is a necessity in order to answer industrial needs (quality control at the end of production lines) and societal needs (expectation projected on the objects of sensation of reliability, naturalness or aesthetic). This measurement need is getting more complex with the arrival of new effects like sparkle in automotive, iridescence in cosmetics, mat in silverware and ceramics. The measurement of appearance solicits several scientific fields: metrology, spectrophotometry, psychophysics and statistics. It is a proactive sector. Today, several measurement instruments exist but they usually characterize the visual appearance only partially. Other devices are currently being developed. At the highest level, National Metrological Institutes are working in order to develop new references, new transfer artefacts, new measurement protocols and even new quantities! This paper aims to give an overview of this specific metrological field. Metrology of appearance is a branch of photometry.