This chapter introduces microwave remote sensing as based on Maxwell’s equations. Maxwell’s equations are important to understand microwave technology. In this perspective, the chapter proceeds to grant a scientific clarification of Maxwell’s equations and their mathematical and physical characteristics. It also demonstrates that electromagnetic wave characteristics are a function of the Maxwell’s equation. In this regard, all electromagnetic phenomena can be said to follow from Maxwell’s equations. In relation to relativity theory, Maxwell’s electrodynamics can be formulated in terms of Minkowski space-time.