Thermals are possibly the most important and versatile items of clothing you can take on any hiking, trekking, camping or travel adventure. They can be worn discreetly underneath clothing as an extra layer of warmth or worn by themselves as comfortable sleepwear.
Available in both synthetic and merino fabrics, both of which have their benefits, Thermals are lightweight and compact so they won't take up much space in your rucksack. They are designed to fit close to your body so they act as another layer to trap warmth right up against your skin.
Merino fabrics are the most comfortable to wear, they don't have the itchiness that we often associate with woollen garments, and the merino fibre helps to regulate your body temperature, making them suitable for both hot and cold climates. The other big benefit of Merino garments is that they resist the build-up of bacteria, which in turn means less smell (think less washing).
Synthetic or polypropylene thermals have been around for decades, you may even be able to say centuries. They are lightweight, warm and dry quickly making them the preferred option for environments where you know you will be wet all day, or activities such as canyoning or kayaking. Synthetic garments do get smellier quicker, but on the flip side, they dry quickly too so freshening them up isn't an overly difficult and long-winded activity.