Animals often use two or more of these mechanisms together to produce the colours and effects they need. Animal coloration has been a topic of interest and research in biology for centuries. In the classical era, Aristotle recorded that the octopus was able to change its coloration to match its background, and when it was alarmed. In his 1665 book Micrographia, Robert Hooke describes the ``fantastical'' (structural, not pigment) colours of the Peacock's feathers:
Aristotle
Robert Hooke