In this talk we will introduce Gromov's $h$-principle theory from a basic and accessible perspective. We will motivate it through visual examples with special emphasis on the method of Convex Integration. Many problems in Differential Topology involve differential relations (differential equations, inequalities, etc.). In many contexts, it can be proven that there exists an $h$-principle: this means that the resolution of certain geometric problems can be reduced to studying the underlying Algebraic Topology. We will show how these techniques can be applied to the study of maximal growth distributions on smooth manifolds. Prototypical examples of these objects are Contact and Engel structures.