ONE OF THE BIGGEST CHALLENGES COMES IN HEALTHCARE, WHERE ENGINEERS LITERALLY HAVE TO MATCH NATURE. ENGINEERING SOME DEVICE THAT WILL HAVE TO FULFIL THE SAME FUNCTION AS A NATURAL PART OF THE BODY OR COORDINATE WITH NATURAL PROCESSES IS ABOUT AS DIFFICULT AS IT GETS. AND REPLACING MISSING OR LOST LIMBS PROVIDES SOME OF THE MOST STRIKING EXAMPLES OF THE PROGRESS WE HAVE MADE.