Non Relativistic Quantum Mechanics
We describe matter with a wave function, $\psi(x)$ in a Hilbert space. The wave function evolves via the Schrodinger equation. Its absolute square gives the probability distribution under a measurement.
To construct the Schrodinger equation, one needs the Hamiltonian of the system. This comes out of classical mechanics.
(1)\begin{align} \dot \psi = i\hbar \frac{d\psi}{dt} \end{align}