K?rastase, Densifique (S?rum Jeunesse 120ml) Inspired by stem cell science, this formula improves and maintains the density of thinning hair, giving it a more volumised and denser feel after the first application. After three months, density of thinning hair is noticeably increased and hair is more manageable.To use: Divide hair into 5 partings, spray along each parting directly onto scalp. Rub in, then spray onto the lengths of the hair.