On a hot night, what makes the biggest difference is how much air can actually move through the fabric. Muslin is woven loosely, with small gaps between the threads, so it doesn't sit heavy and trap heat the way tighter weaves can. That's the whole reason we build our pyjamas from it. It's also lightweight, so it doesn't add bulk under a blanket or sheet, and it dries quickly if you're doing a lot of night laundry.
Ours are two layers of muslin cotton, and we get asked sometimes if double layer means double heat. It doesn't work that way here: the weave still has its open structure, so air keeps moving. Each pair is pre-washed before it ships, so the fabric is already soft on the skin, not stiff out of the bag. We sew with flat seams so there's nothing scratchy rubbing at night, and we use child-safe dyes with no harsh finishes. Sizes run from newborn up to around 4 years.
A couple of care notes: wash cold on a gentle cycle, and tumble dry low or hang to dry, and skip fabric softener and high heat. Muslin creases easily, that's normal for the weave, and it gets softer with every wash, so don't worry if it looks a little rumpled straight out of the dryer. We ship worldwide with tracked delivery, and if it's not right for you, unworn returns are accepted within 30 days.