Personalized Smart Biological Engineer Toddler Long Sleeve T-Shirt. Biological engineering, the profession for intelligent people text with the letter E in the engineering wearing a hard hat is a funny design with attitude for engineers and college students 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.