In these introductory lectures I will give a brief introduction into generic features of theories with extra dimensions. Topics that we will touch are so-called Kaluza-Klein towers of new particle states, the expected modification of Newton's gravitational law at small distances as well as the variation of fundamental constants with space or time. I will explain in some detail the phenomenological challenges that arise for vector or fermion fields fundamentally 'living' in more than three spatial dimensions, and how orbifold compactifications can address these issues. Depending on time, I will also provide some historical context of various extra-dimensional theories, and maybe add some more detailed remarks about a very concrete model that was popular until a few years ago, namely the idea of the entire standard model living in more than just 3+1 dimensions.
This event is part of the master lecture series organized by the Section for Theoretical Physics.