Personalized Smart Biological Engineer Youth 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. youth long sleeve t-shirt. Shoulder-to-shoulder taping. Youth: S(6/8), M(10/12), L(14/16), XL(18/20)