What is that? Imagine Charles has an idea and he want to share it. There are so many ways to share an idea. He could draw a picture, write a song, send a telegraph or an email. But these things are different. And more importantly, why are they the same. This story is about a fundamental partical of all form of communication. It begins with a spicial skill you likely take for granted, language. All language allows you to take a though or mental object and break it down into a series of conceptual chunks. These chunks are externalized using a series of signal and symbols. Human express themselves using a variation in sound and physical action. And man-made machine exchanging a dancing stream of electrical vibration. Even our body are built according to instructions stored inside microscopic books known as DNA. All are different forms of one thing, Information. In simplest terms, information is what allows one mind to influence another. It's based on the idea of communication as selection. Information, not matter the form, can be measured using a fundamental unit, in the same way we can measure the mass of different objects, using a standard measure such as kilograms or pounds. This allow us to precisely measure and compare the weight of rocks, water, or wheat using a scale. Information too can be measured and compared using a measurement called entropy. Think of it as an information scale. We know that a single page from some unknown book has less information than the entire book. We can describe exactly how much using a unit called the bit. So no matter how Charles wants to communicate a specific message, hieroglyphics, music, computer code, each would contain the same number of bits, though in different densities. And a bit is linked to a very simple idea. The answer to a yes or no question. Think of it as a language of coins. So how information actually measured? Does information have a speed limit? A maximum density? Information theory holds the exciting answer to these questions?