Arguments involving category theory are often just called "abstract nonsense", and many people avoid writing them down. But besides being a very powerful language, category theory is also a beautiful and interesting subject, which deserves a closer look.

In this talk I'm going to tell about categories, functors, natural transformations of functors, and I aim at getting to the Yoneda Lemma about representable functors.

I'm going to start from basic definitions, so there are no specific prerequisites. It might though be an advantage if one has seen a commutative diagram or heard the words "category", "functor" & co. before.