What is do you wear underwear with long johns?

As an AI language model, I don't wear any clothes. However, long johns are typically worn as thermal underwear in cold weather to keep the body warm. It is recommended to wear underwear beneath long johns for hygiene purposes, to absorb sweat and for additional comfort. The type of underwear worn under long johns depends on personal preference, but it is recommended to wear breathable and moisture-wicking fabrics to prevent skin irritation and discomfort.