Merino wool makes a great base layer. It's lightweight and naturally resists moisture and odours while keeping your temperature regulated.
It's soft and comfortable and the perfect fabric for wearing right next to the skin. It's our favourite material for sweaty winter commutes because of its low bulk and weight, and you can pretty much last the week without having to wash it. It's also a great one to wear through the year be it camping or travelling. You don't have to worry about washing the Merino wool because it can be machine washed at 40°C and will also withstand a low tumble dry without problem.
Along with Howies, Rapha make the best super-fine Merino bases. Their sleeveless version is particularly adaptable to the seasons and can be worn all year round through hot and cold. The sleeveless version costs £40 and the short-sleeved £45 and the long sleeve £50.