Professor Jim Al-Khalili traces the story of arguably the most important, accurate and yet perplexing scientific theory ever: quantum physics. The story of quantum physics starts at the beginning of the 20th century with scientists trying to better understand how light bulbs work. This simple question soon led scientists deep into the hidden workings of matter, into the sub-atomic building blocks of the world around us. Here they discovered phenomena unlike any encountered before - a realm where things can be in many places at once, where chance and probability call the shots and where reality appears to only truly exist when we observe it. Albert Einstein hated the idea that nature, at its most fundamental level, is governed by chance. Jim reveals how in the 1930's, Einstein thought he'd found a fatal flaw in quantum physics. This was not taken seriously until it was tested in the 1960s. Professor Al-Khalili repeats this critical experiment, posing the question does reality really exist, or do we conjure it into existence by the act of observation? Elsewhere, we explore how the most famous law of quantum physics The Uncertainty Principle is obeyed by plants and trees as they capture sunlight during the vital process of photosynthesis. Could quantum mechanics explain the greatest mystery in biology - evolution?