In 1976, a British pop band called the Kursaal Flyers released a single called “Little does she know.” It was their only top 20 hit in the UK and it made use of a very simple form of recursion.
The song begins with the following lyric:
“Little does she know that I know that she knows that I know she’s two-timing me.”
You could just keep saying “she knows that I know that” over and over again forever (never finishing the sentence) and still be producing a perfectly grammatical sentence. Try it. It’s fun — for a short time. Unfortunately, it obviously doesn’t make much sense. You are ultimately wasting your own and everybody else’s time.
Still, you get the idea of language’s infinite creativity. There may be practical limits, but we are able to use language to say whatever we want.