Mesenchymal stem cells are cells that we have as adults, which have the potential to become fat, bone, and cartilage tissue. These present an attractive therapeutic option for the regeneration of aforementioned tissues. Hydroxyapatite is a material that is used to coat titanium joint replacements in an effort to improve how the cell interacts with the surface. This image was coloured in using a technique called energy dispersive x-ray spectroscopy, which allows us to visualise where certain elements are in the sample. In red, carbon, and in green, calcium. The carbon should only occur in cells, whilst the calcium makes up the bulk of the hydroxyapatite.