How to make text automatically expand/shrink in a layer (div)?

Question

User interface

Suppose I have a DIV on my site, a regular layer.
For example 300 by 200 pixels.
And in this layer I display different text.
Sometimes big, sometimes not so much, generally from 5 words to a small paragraph of 25-30 words.
How (preferably via CSS) can I make the text automatically resize to the size of the DIV and be displayed occupying the entire layer, but the DIV itself should not change in size?
Those. if there is only one word, it is large and is displayed in a large font; if it is a sentence, the text size is already smaller, and everything fits into the layer.

Answer 1

Use relative units for text: rem, em, %