A type of extracellularly deposited substance composed of an amyloid protein and additional components including HEPARAN SULFATE PROTEOGLYCAN; LAMININ; COLLAGEN TYPE IV; SERUM AMYLOID P-COMPONENT; and APOLIPOPROTEINS E which together form characteristic amyloid fibrils. The core of amyloid fibrils is formed by the stacking of overlapping beta-pleated sheet domains of the amyloid protein. There are many different amyloid proteins that have been found forming the core of the fibrils in vivo. However, amyloid can be formed from any protein that exposes beta-pleated strand conformations during unfolding or refolding. A common characteristic of amyloid is the ability to bind such dyes as CONGO RED and thioflavine.