Muslin isn't a type of fiber, it's a way of weaving cotton. The threads sit further apart than in a tighter weave like poplin or denim, so the fabric stays open and light. That open structure is what lets air move through it and helps it dry fast after a wash. Some fabrics sold as "muslin style" are actually polyester or a cotton blend, so if you're comparing options, check the fabric content on the label. Ours is cotton.
Our clothes are made from two layers of muslin cotton stitched together, not one. We pre-wash the fabric before it's cut and sewn, so it arrives soft instead of stiff and needing a few washes to break in. Seams are sewn flat so there's less rubbing against the skin, and the dyes are chosen with kids in mind. We don't add coatings or harsh finishes to the fabric.
Cotton like this creases easily, especially straight out of the wash and dry cycle. That's just how the weave behaves, not a flaw. Wash cold on a gentle cycle, tumble dry low or hang to dry, and skip the fabric softener, it coats the fibers and works against the way cotton softens naturally over time. We carry sizes from newborn up to around 4 years, ship worldwide with tracked delivery, and take unworn returns within 30 days.