Apparently a team of researchers in Japan has isolated the gene in the onion which produces the chemical that causes tears when the onion is cut. (Tearless Onions May Be on the Way (washingtonpost.com)) They're hoping they can engineer a new onion which lacks the gene, so that onions can be tear-free without any taste changes. My favorite quote from the article:

In fact, stopping the tears might mean altering the flavor in unpredictable ways, said Eric Block, an expert in the chemistry of onions at the State University of New York at Albany.

What I love about this is the idea that somewhere out there, there are people who are experts in "the chemistry of onions". I mean, is modern science great or what?