Bioluminescence describes the light that some living creatures such as fireflies and jellyfish emit from their cells. Harnessing these reactions has already transformed key areas of clinical diagnosis and medical research. But scientists are now looking at whether this "living light" could help enhance food crops, detect pollution or even illuminate our journeys home. On a night in January 1832, off the coast of Tenerife, a young Charles Darwin wandered up on to the deck of the HMS Beagle.(BBC News)