Onions can make even the strongest man cry. Why? It is a very technical explanation, but basically, it boils down to a bit of a chemical reaction between your eyes and the onion. An onion sitting on the counter is fine, but the second you begin chopping it up, you are starting a chain of events in the kitchen. Amino acid sulfoxides are transformed into sulfenic acids as the cells are broken during the slicing and dicing process. This results in the release of propanethiol S-oxide, which is the vapor that wafts up and into your eyes. Once the sulfuric acid compound hits the natural tears in your eyes, things really get bad and the end result is sulfuric acid. Your poor eyes fight back the only way they can and produce more tears to try and wash away the nasty acid. You end up crying. Once the onions hit the frying pan or begin cooking, the enzyme that had you bawling is neutralized. Although there are plenty of tips and tricks that have been passed down through the years, there are only a few that actually work. Refrigerate your onions before cutting, wear safety goggles or cut the onion under running water.