Personalized Heart Elements Toddler Long Sleeve T-Shirt. A heart filled with Chemical Elements and their symbols is a unique chemistry design for students, teachers, chemists and chemical engineers. A classic for Fall, Winter and Spring, these long sleeve toddler t-shirts are sure to be a staple in your child's wardrobe. Whether layered or alone, this t-shirt is soft yet durable enough to stand up to your toddler's playtime demands.