Miniature heart inventor: Breakthroughs take time to sell

Professor Ronald Li is the inventor of tiny human hearts. Grown from stem cells, they beat exactly like hearts and they are designed to test the safety of new medicines.

Prof Li formed a company called Novoheart to market them to the world's pharmaceutical firms.

Having taken 20 years to develop the miniature heart, he says he may have to wait years longer before the world wakes up to this new technology.

Video journalist: Jeremy Howell