Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Problem:Passage: The human brain is an amazing organ. It is the most complex organ in the human body. By adulthood, the brain weighs about 3 pounds and consists of billions of neurons. All those cells need a lot of energy. In fact, the adult brain uses almost a quarter of the total energy used by the body!. Answer: brain
Solution:
What is the most complex organ in the human body?