One of the large multinuclear cells in growing bones concerned with bone resorption (dissolution and absorption of osseous tissue). They have 5 to 20 nuclei, but some may have as many as 200 nuclei), and were discovered by Rudolf Albert von Kolliker (1817-1905) in 1873. Due to their role in bone resorption, they are crucial to the remodeling of bones that takes place during normal development, as well as mediating bone loss in pathological conditions (e.g., osteoporosis). They are one of the three cells involved in the development, growth and remodeling of bones. The other two are osteoblasts (bone-forming cells) and osteocytes (mature bone cells). While the main function of osteoclasts concerns bone resorption, they also have a number of other documented functions (e.g., regulating the function of other cells such as osteoblasts). .