Complex sentence: Freshly cut onions often cause a stinging sensation in the eyes of people nearby, and often uncontrollable tears.this is caused by the release of a volatile gas, "syn"-propanethial-S-oxide, which stimulates nerves in the eye creating a stinging sensation.
Split into simpler sentences: Freshly cut onions often cause a stinging sensation in the eyes of people nearby, and often uncontrollable tears. This is caused by the release of a volatile gas, "syn"-propanethial-S-oxide, which stimulates nerves in the eye creating a stinging sensation.