On closer inspection the sand is actually made up of tiny broken up shells which is where the colour comes from. (travellermade.com)
By comparison, microfracture, a surgical technique that involves creating tiny breaks in a bone, bathes an injured joint in a few hundred thousand stem cells. (denverpost.com)
Or they can create tiny breaks in the underlying bone in the hopes of releasing progenitor cells that can restore the cartilage. (sciencemag.org)