In the previous chapter, we studied Hamiltonian mechanics. In this chapter, we will show how to use Hamiltonian mechanics to transition from classical mechanics to quantum mechanics. We will use the quantization of a simple harmonic oscillator (SHO) as an example. If readers do not have a strong background in quantum mechanics, they are advised to revisit wave mechanics and matrix mechanics treatments of SHO. However, just like how we studied Lagrangian mechanics and Hamiltonian mechanics in the previous chapter, our goal is only to learn the skills and rules of performing quantization and promoting a variable to an operator.