Quantum mechanics, which is the branch of physics that describes the behavior of particles at the quantum level, represents a fundamental framework for understanding the behavior of matter and energy at very small scales. It provides a powerful and accurate description of physical phenomena, especially in the microscopic realm.
However, it's important to note that quantum mechanics is not considered the "last level" or the "beginning of existence" in the sense that it explains everything about the universe or provides a complete understanding of reality. While quantum mechanics is incredibly successful in describing the behavior of particles and fields, it is also known to be incompatible with our current understanding of gravity, as described by Einstein's general theory of relativity.
There is an ongoing quest in theoretical physics to develop a more comprehensive theory that can reconcile quantum mechanics and general relativity into a unified framework, often referred to as a "theory of everything" or a "quantum theory of gravity." Such a theory would be able to describe phenomena at all scales, from the subatomic to the cosmic.
It's worth noting that our understanding of the universe is continually evolving, and scientific exploration and discovery are ongoing. While quantum mechanics provides a deep understanding of the microscopic world, there are still many mysteries and unanswered questions about the nature of reality, the origins of the universe, and the fundamental laws governing it. The exploration of these questions remains an active area of research in physics and other scientific disciplines.