The microscale phenomenon is not different from the macroscale phenomenon, and it is mainly governed by the kind of fluid used. In the case of rarefied gases, continuum assumption is not valid. However, in other cases such as microchannels, where liquids are used, the continuum equations can be used to analyze the flow physics. In the microscale regime, an interesting physical phenomenon, which is entirely different from that in the macroscale, can be observed. This unusual phenomenon can be demonstrated through the study of microscale energy transport. Section 6.2 mainly focuses on gas flows in microchannels as the deviation from the continuum in the microscale is primarily for gases.