Flow-based programming is an example that's a bit easier to understand and toy with:

https://en.wikipedia.org/wiki/Flow-based_programming

Lambda Calculus in its many forms is probably the original:

https://en.wikipedia.org/wiki/Lambda_calculus

Here's an example of its (i.e. LISP's) power in bootstrapping a whole toolchain with several languages starting with assembly and LISP:

https://speakerdeck.com/nineties/creating-a-language-using-o...

Also used in hardware design for integration with software:

http://scheme2006.cs.uchicago.edu/05-saint-mleux.pdf