Cambridge Discovery Education Interactive Readers are the next generation of graded readers - captivating topics, high-impact video, and interactive exercises designed to motivate and engage. The human brain is an amazing organ controlling our speech, making our heart beat, and solving problems. Come and explore how our brains work and make us who we are. Use the unique code inside the book to access the online reader, complete with videos and interactive exercises. Word count: 2319. Lexile reading level: 980L.