Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change colour as the angle of view or the angle of illumination changes.
Examples of iridescence include soap bubbles, butterfly wings and sea shells, as well as certain minerals. It is often created by structural coloration (microstructures that interfere with light).
The word iridescence is derived in part from the Greek word ἶρις îris (gen. ἴριδος íridos), meaning rainbow, and is combined with the Latin suffix -escent, meaning "having a tendency toward". Iris in turn derives from the goddess Iris of Greek mythology, who is the personification of the rainbow and acted as a messenger of the gods. Goniochromism is derived from the Greek words gonia, meaning "angle", and chroma, meaning "colour".