Thermal capacitance describes the capacity of a material to store heat energy. It is often viewed as the analogy of material mass in transient structural analysis. Transient analysis means analyzing a system in unsteady-state: a state varies with respect to time. A transient thermal analysis solves problems like, how long can the inner side of a steak on grill reach a certain temperature, or, what is the temperature over a hot pot after a certain time. In this course, we will explore how transient thermal analysis is structured with the thermal capacitance term and explain the different parameters related to thermal capacitance. We will also give a discussion on phase change, which is a special process for materials to transform between different phases under the effect of temperature.