In the first introductory part, we start by reviewing some basic aspects of equilibrium calorimetry.  In particular, we illustrate the presence of a Schottky anomaly and the validity of the Nernst Postulate for the simplest two-level system.  We use that two-level system to open the avenue toward nonequilibrium calorimetry by introducing the two-level switch (agitated qubit). We show how to compute the heat capacity there by solving the Poisson equation sourced
by the excess heat.