Take challenge of our free science quizzes and riddles! These free quizzes produce better organization of knowledge by helping the brain organize material in clusters to allow better retrieval. Riddles are also a great way to challenge your brain and help it grow more! Just like the muscles in your body, the more you use them, the stronger they get. This is how your brains is; the more work out you give it, the more flexible, stronger, and faster it gets.