The artwork is absolutley stunning. The material is polyester, which is not only warm, but water resistant and quick dry. The inside is lined with a softer polyester, kind of like fleece, but lighter. I do have to wear a shirt under it because the zipper is uncomfortable against my skin. For sizing, I was unsure—I am in between a small and medium in women’s sizing and and this is unisex, so I went small. It fits me perfectly at 5’4” and 125lbs, but it is a slim fit on me. It fits exactly like the model pics I’d say, but only feels slim when I’m doing yoga, etc. I thought about sending it back for a medium to have a looser fit, but after wearing it a few minutes decided to keep it the way it is-I don’t like bulky clothing. But I’d say if you’re my size or a little bigger and you want a loose fit, go medium. The material is stretchy too, so I am able to do yoga in it no problem. Lounging around the house is more fun in this onesie!