Within quantum mechanics (QM), there is a similar procedure for dealing with small systems. We start by writing down a Hamiltonian operator and find its eigenvalues and eigenstates. Then, choosing an arbitrary t=0microstate and expressing it as a linear combination of eigenstates, we can use Schrodinger’s equation to predict the microstate of the system at a later time t. Once the microstate is known, the probability to obtain a certain measured value of any observable can be calculated.