Kids Organic Undies Woollykins Buy Children's Plus Velvet Thermal Underwear Baby Autumn and Winter Organic Baby Clothes Australia Organic Kids Clothing Elves Kids Organic Cotton Underwear Sustainable Handmade Toddler Etsy. Our children's underdress Ylvi is the little sister of our Under Dress Freya and together with our Children's Over Dress Ylva completes the outfit for inquisitive little adventurers. The untreated fabric made of pure cotton is not only comfortable to wear, but also robust enough to meet the special requirements of childlike adventurousness.