This is how the levitation works. Inert, magnetic nanoparticles are inserted into the cells, and researchers can manipulate them by using magnets--in this case, a magnetic "pen." That ability to tinker with the cells opens the door for more complicated cultures. The four-layered replication, of the lung's bronchiole tissue, is made from endothelial cells, smooth muscle cells, fibroblasts, and epithelial cells. Arranging those cells in the same way as lung tissue has never been done before, and the researchers say it's the closest anyone's gotten to real bronchiole tissue.