Personalized Quantum Mechanics Building Toddler Long Sleeve T-Shirt. Quantum Mechanics Building text with a floor plan and the you are here arrows pointing to 2 different spots. Particles can be in two different places simultaneously. Can You? A humorous physics design for your favorite student, teacher, engineer or scientist at birthdays and holidays. 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.