Type I collagen is the major constituent of the organic matrix of bone tissue. Collagen makes up as much as 70% and 90% (w/w) of the organic matrix in cancellous bone and compact bone, respectively. 1 Depending upon the age of the specimen, collagen type I molecules form differently sized fibers. In humans, cross striated collagen fibers of infant bone have a diameter ranging from about 20 to 60 nm, while fibers with a diameter up to 150 nm are characteristic of the bones of mature individuals. 2