At the beginning of the 20th century, the wave theory of light was facing insuperable problems. The ultimate death blow was Einstein’s explanation of the photoelectric effect. ‘Quantum waves’ discusses the work of Louis de Broglie, Niels Bohr, and Einstein. It considers the uncertainty and indeterminacy of electron motion, wave function, quantum tunnelling, and the phenomenon of entanglement. Quantum theory shows that electromagnetic radiation and electrons are particles. If string theory is correct, it shows that the wave concept is much more than a powerful tool to model the way the world works. It means that, for all its staggering complexity, the Universe is nothing more than a vast network of interacting waves.