In this episode, we learn about the skeletal system and why astronauts Scott Kelly and Mikhail Kornienko are out in space studying it. We review the anatomy of the skeletal system, including the flat, short, and irregular bones, and their individual arrangements of compact and spongy bone. We also review microanatomy of bones, particularly the osteons and their inner lamella. Finally, we learn about the process of bone remodeling, which is carried out by crews of osteocytes, osteoblasts, and osteoclasts.