Underwear / Thermals
Thermals are the inner layer of your clothes when you are skiing or snowboarding, and they are designed to absorb the sweat and moisture away from your body so that you don't get cold. Thermal underwear is a must when you are snowboarding or skiing on a cold winter day, but they can also be used for active training, running on cold days etc. Ski thermals typically consist of a t-shirt with long sleeves and a pair of long underpants.
Choosing the right thermals
Fabric made from synthetic fibers (polypropylene or polyester) would be a good choice. These materials are light, generally well-fitting on your body, comfortable to wear and at the same time moisture transporting, which means that it draws the moisture and sweat away from the body and keeps your body dry throughout a whole day in the snow. Thermal underwear are made from synthetic materials that dry up faster than other materials like wool for instance. T-shirts and long underpants made from wool are very good for keeping you warm, even when they are wet, but can sometimes be uncomfortable and itchy to wear. Very often the fabric is a combination of synthetic fibers and wool to improve the drying abilities and comfort of the ski thermals.
It is a good idea to bring a couple of extra sets of ski thermals for the trip. After using it for a few days it will need to be washed due to hygienic reasons.