So we switched our models, and now we began to look for skeletal stem cells. And to cut again a long story short, about five years ago, we found these cells. They live inside the skeleton. Here's a schematic and then a real photograph of one of them. The white stuff is bone, and these red columns that you see and the yellow cells are cells that have arisen from one single skeletal stem cell -- columns of cartilage, columns of bone coming out of a single cell. These cells are fascinating. They have four properties.