Collagen is a tissue culture substrate superior to glass and plastics, and possesses the unique interaction characteristics with cells. Fibronectin is supposed to be a substance important for cell adhesion to collagen. Collagen fibril (quarternary collagen structure) has the specific interaction with cells to control the migration, alignment and differentiation of cellls. Collagens, purified from bone and tooth induce bone formation when implanted subcutaneously. Collagen fibril lattices constructed with recipient epidermal cells are well integrated into skins of experimental animals. Collagen as a biomaterial having specific interaction properties against cells would be more important as hybrid artificial organs are developed.