Illustration of the crystalline structure of the fibrillin-1 domain. Fibrillin-1 (orange) is a glycoprotein component of the extracellular matrix. It is essential for the proper formation of the extracellular matrix, as it forms long microfibrils that are very important for the formation of elastic fibres. The extracellular matrix not only functions within the connective tissue, but it also plays an important role as a reservoir for growth factors.