Snow sock
Contrary to what you may think, the choice of socks is very important, without a specific ski/snow sock, your boots will not be as effective.
Socks also play an important role in your comfort and performance.
Choose natural materials, such as wool, merino or silk, which have both breathable and insulating properties and keep your feet warm and dry. Specific ski/snow socks made of synthetic material can be effective even if they are a step down, depending on what you are looking for in terms of product range.
Cotton socks should be avoided as they do not absorb moisture (wet feet = cold feet). Thicker socks and wearing 2 pairs of socks reduce your sensation, compress your feet and decrease blood circulation which makes your feet cold and numb and increases the feeling of cold.
TIP Remember that the outer shell of the boots is thick and together with the inner lining they provide good insulation.