The squiggly lines you're referring to in the nucleus of an animal cell are called chromatin.

Here's a little more about chromatin:

* What it is: Chromatin is a complex of DNA and proteins that make up chromosomes.

* Structure: It appears as a tangled mass of threads or squiggly lines when viewed under a microscope.

* Function: Chromatin's main role is to package DNA in a way that fits inside the nucleus and allows for the regulation of gene expression.

Think of it like this: Imagine you have a very long string of yarn (DNA). To make it easier to handle, you wrap it around a spool (proteins). The spool with the yarn is the chromatin, and it helps keep the DNA organized and functional.