Resumen: In this Final Degree Project, we not only address the classical question of dynamics reaching consensus but also opinion plurality in social systems. We will propose different mathematical approaches to provide insight into the transition between global consensus and the emergence of polarized states and echo chambers. Empirical evidence points to both social influence and controversy of the subject matter as the main elements that promote this transition, both off and online arguments. Therefore, it is critical to use these two elements to describe the rise of polarization and echo chambers. With this purpose in mind, we will start by characterizing social systems as complex networks where social phenomena emerge from the pattern of interactions between humans. Our focus is on creating simple models that can reproduce complex macroscopic social outcomes from reasonably easy rules of behaviour on the fine scale.