By the end of the nineteenth century, physicists had developed working theories to explain most of the questions relating to the observable world. In 1900, Max Planck set out to answer a simple question related to light bulbs. He had no idea his work would open the door to a new branch of physics, Quantum Mechanics. This volume explains the exciting scientific discoveries made at the dawn of Quantum Mechanics. Students will be fascinated by the important work being done the world's most distinguished physicists, many of them contemporaries, including Planck, Albert Einstein, Niels Bohr, and Marie Curie.