The vegetable known to make people cry is the onion. When cutting onions, cells in the onion are damaged, leading to the release of enzymes and sulfur compounds. These compounds react to form a gas called propanethial S-oxide, which can irritate the eyes. This irritation leads to the release of tears as a protective response. Different types of onions can have varying levels of pungency, with some causing more tears than others. Various methods exist to minimize crying while cutting onions, such as chilling them beforehand or using specialized cutting tools.