Category Theory 1.2 by Bartosz Milewski.
Brief notes on the first couple of minutes:
Our toolset includes:
Abstraction – lose the details – things that were different are now the same
Identity – what is identical or considered to be identical
Composition and Identity define category theory.
Despite the bad press about category theory, I was disappointed when the video ended at the end of approximately 48 minutes.
Yes, it was that entertaining!
If you ever shied away from category theory, start with Category Theory 1.1 and follow on!
Or try Category Theory for Programmers: The Preface, also by Bartosz Milewski.