In the final part of the series celebrating Einstein's great work of 1905, Brian Cox explores the confusing world of quantum mechanics.
Back in 1905, Albert Einstein proposed his own quantum idea to describe the consistency of light.
In the photo-electric effect paper, which was eventually to win him the Nobel Prize, Einstein proposed that light was made up of tiny particles (quanta of light) which today we call photons.
However, as quantum theory took off and developed in the 1920s and 1930s, Einstein grew increasingly uncomfortable with some of its propositions, which introduced the importance of chance and randomness into physics.
Einstein famously said that God does not play dice with the universe.
Brian Cox talks to scientists including Sir Roger Penrose and Professor Michio Kaku about Einstein's objections to quantum mechanics and he also travels to Vienna to meet Professor Anton Zeilinger who has used quantum theory in teleportation.