Artist Tom Phillips takes casts of human skulls and then cover them in his own hair clippings:
A work in (slow) progress features two casts of the skull covered in my own hair. Now at the transition stage on the way to the bus-pass years my pepper and salt hair represents all phases of my life past and (D.V.) future: the dark brown of youth can still be collected from my head whereas my beard yields almost pure white. The first of two projected works is shown in its present form; awaiting further growth. It represents the old artist meeting his younger self coming the other way, a sort of Bonjour, Monsieur Tom.
http://www.tomphillips.co.uk/sculptur/skulls/index.html (via Proceedings of the Athanasius Kircher Society)