I wear all merino (tshirts,underwear, long underwear, shirt layers, pants socks, hoodie) except for my outermost layer which I switch up to different things depending on conditions due to the thermal performance. I have been doing this for 5+ years now. It temp regulates, I wear wool tshirts often in the summer and wool socks year round (thin in the summer). Ice fishing this winter in 7deg. temps I had to go in after my dogs. It was a shallow river set back and the short story is that I had to break through the ice and wade out to the dog in 4' of water and get her on the good ice. It was a 10 min. walk back to the truck and by the time I got back to the truck I was overheating. I wear all wool under my ice fishing bibs and jacket as well and was amazed how warm it kept me after wading in chest deep 33 deg. water then walking soaking wet in 7 deg. temps.. I knew that wool keeps you warm when it wet, I just had never put it to the test in these low temp conditions as I like to stay dry when ice fishing.