The infinitesimal has fascinated mankind for centuries. And it was one of the ancients who first hit upon the idea of matter as being comprised of atoms - a theory which would take more than 2000 years to test. This book by the prominent science and science fiction writer, Isaac Asimov, provides a survey of what is known about sub-atomic physics. Starting with the question of what happens if material is divided ad infinitum, he advances into the worlds of atoms and their nuclei, of light, electricity and energy, of quarks, neutrinos, antiparticles and other atomic components which explain the theory of everything and how the universe began.