Cold is here, and we need to address the undershirt. Typically an A-shirt (wife beater) or a vest if you’re British, and often a T shirt, when it gets colder a longsleeve shirt works best. The henley is a nice option, as you can vent the neck/chestal region via buttons, but on colder days a crewneck thermal is perfectly welcome.
Wings + Horns has this thermal undershirt, for just such an occasion. For those of us on a budget, a waffle-material long underwear shirt works just fine too, and costs about $5. via Selectism.