 The Titans are giant humanoid figures about 3 – 15 meters ( 10 – 50 ft ) tall and are usually masculine in body structure but lack reproductive organs . Although they do not appear to need food , they instinctively attack and eat humans on sight ; it is mentioned that they derive their energy from sunlight . In addition the Titans also do not have a proper digestive tract ; once they have eaten their fill of human prey , titans will vomit their meal into large , slimy balls , derisively referred to as " hairballs " . Finally , their skin is tough and difficult to penetrate , and they regenerate quickly from injuries , save for a weak spot at the nape of their neck . 
