Why is it interesting?

The Yoneda lemma is "arguably the most important result of category theory" (source).

Layman

Informally, [the Yoneda Lemma] implies that you can gain information about an object by viewing it from *all* possible angles. That kinda makes sense, right? To put it another way: a mathematical object is totally determined by its relationships to other objects. It's sort of like the old saying, “Tell me who your friends are, and I’ll tell you who *you* are.”Math3ma

• http://www.math3ma.com/mathema/2016/9/12/the-most-obvious-secret-in-mathematics
• http://www.math3ma.com/mathema/2017/8/30/the-yoneda-perspective

Student

• http://www.math3ma.com/mathema/2017/9/6/the-yoneda-embedding
• http://www.math3ma.com/mathema/2017/9/14/the-yoneda-lemma

Researcher

Examples

Example1

Example2:

FAQ

History