Type I collagen composes 90–95% of the organic matrix, with remainder of the matrix being a homogenous liquid called ground substance consisting of proteoglycans such as hyaluronic acid and chondroitin sulfate ,[18] as well as non-collagenous proteins such as osteocalcin, osteopontin or bone sialoprotein . Collagen consists of strands of repeating units, which give bone tensile strength, and are arranged in an overlapping fashion that prevents shear stress. The function of ground substance is not fully known.[18] Two types of bone can be identified microscopically according to the arrangement of collagen: woven and lamellar.