Since Planck discovered quantization in 1900, the nature of quanta was a mystery. That problem is solved in this book. We derive the postulates of quantum physics from the equivalence principles, gravity and relativity, by analyzing the vacuum. We clarify various conundrums of quanta: - We derive nonlocality. - We find the origin of the Schrödinger equation. - We find the origin of the probabilities of quanta. - We find the basis of the Planck constant h. - We find a generalized Schrödinger equation. - We find the origin of quantum gravity. - We discover how quanta, vacuum and curved space are related. Using the concepts of space, time, gravity and vacuum, we discover how vacuum propagates at the velocity of light. We realize how that propagation causes quantization. We apply that propagation to the calculation of the density parameter ΩΛ of the vacuum of the universe. Our result is in precise accordance with observation, whereby we do not apply any fit. Invited to discover the nature of quanta are classes from grade 10 or higher, courses, research clubs, enthusiasts, observers, experimentalists, mathematicians, natural scientists, researchers …