Just 45 years ago, the age of gene modification was born. Researchers could create glow-in-the-dark mice, farmyard animals producing drugs in their milk, and vitamin-enhanced rice that could prevent half a million people going blind every year. But now GM is rapidly being supplanted by a new system called CRISPR or 'gene editing'. Using this approach, scientists can manipulate the genes of almost any organism with a degree of precision, ease and speed that we could only dream of ten years ago. But is it ethical to change the genetic material of organisms in a way that might be passed on to future generations?