Finding camping/travelling gear is a serious endeavor. There are very few standards to judging gear, online or even in person, and if you think buying jeans online is hard, you haven't spent hours chatting up folks about glorified fancy underwear. I am pretty close to going and buying every single variation of sleeping bags, small plastic containers and base layers to just stop wasting my time looking online for good clothes.
From what I can gather, base layers (the fancy undies), are a relatively new thing. Everyone knows about those funny Union suit long underwear and those cotton waffle long johns, but the new stuff is "High Tech." Now, if you're like me, you thought that the cotton waffle stuff was good or at least sufficient. But if you tell that to a outdoor sports salesperson, they'll tell you that you're crazy and you will freeze to death and die and it is EVEN WORSE THAN JUST WEARING NOTHING AT ALL. And it kinda makes sense--if you've ever sweated through a t-shirt in the summer and then went into icy cold air conditioning, you realize how awfully cold and clammy your cotton t-shirt can be. Therefore, I've been seeking out definitive advice on undergarments and here is what I've figured out:
Dressing for the elements is divided into three major layers: the outer layer, the insulating layer and the base layer. You could have more than three layers, especially in the insulating category, but the outer protects against the appropriate weather, the insulator, uh, insulates and the base layer is meant to wick away moisture. But!! The base layer can also be the insulating layer, and that's when you get into this awful conundrum of what makes a good base layer.
A lot of real human beings and websites say that there is only scratchy merino wool and a multitude of scratchy, synthetics base layers that have acronyms that aren't pronounceable like: MTC, SNWRW, STE, RKI, &c., &c. (I made most of those up or tried to remember the real ones). But!!! You can also get silk base layer undies! But!!! No one can tell you for sure about how warm they are. Some people say silk makes you cold. Some say it will make you toasty warm when you need to be, and nice and cool when you also need to be. Bamboo and coconut have also been mentioned in the various literature I've found, but it's always in a blend with synthetic fibers or merino wool. It is processed, charred fiber--the logic I've made out of it is that the plant charcoal sucks up odor. So it's not anymore soft (like a hairy, hard coconut) than synthetic fibers.
Then there is the handful of double layered long underwear, that usually consists of a cotton or cotton-blend interior with a merino wool or wool blend outer layer. This obviously negates the first rule of not using cotton against your skin, but who am I to say what works?
Then all the variations: Your base layer can be your only layer, your base layer could be transparent, so you should have a layer underneath your base layer, your insulating layer can also be your base layer (but you should then still be wearing a base layer because your insulating layer won't necessarily wick away moisture), your outer layer can just be a shell or it can be an insulating layer itself. And then everything is some level of elastic-y tightness that swears their interlocking flat design is the best and will not chafe (despite that they are all made out of stuff that is so itchy you don't want to move). &c., &c.
The red butt flap onesie looks very appealing, doesn't it?
So. If you have anything to offer on the base layer debacle, feel free to put in your two cents.