Gravity is a unique phenomenon we all take for granted. However, as simple as free fall may seem, gravity is still a mystery in physics. What is gravity? How does it look between the planets and between small particles? Is there a “graviton,” a quantum particle of gravity? Although the title may want to focus on the gravitons, this book delves into the theory of gravity in layman’s terms. We will explore gravity seen by Newton and Einstein, as seen by Hawking, and eventually rounding up the main ideas of string theory and loop quantum gravity.