[Structure] random nanochannels in spongelike keratin [Example] Diffuse non-iridescent blue of Ara ararauna, blue-and-yellow macaw[48] [Mechanism] 
Deformed matrices
D i f f r a c t i o n g r a t i n g
S e l e c t i v e m i r r o r s
P h o t o n i c c r y s t a l s
C r y s t a l f i b r e s
D e f o r m e d m a t r i c e s
R e v e r s i b l e p r o t e i n s