Personalized Quantum Mechanics Building White Toddler Long Sleeve T-Shirt. Quantum Mechanics Building text with you are here arrows pointing to two different locations is a humorous quantum physics design for science geeks at back to school, birthdays, holidays and graduation. 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.