This is how to make something that looks like the image below.



I'm not sure what use this might be...but it's kind of fun.

This starts with a 640 x 480 canvas.

Do Filters>Render>Clouds>Plasma. Do a sort of middle level on the turbulence, tho you can use higher values. I would avoid really low values.

Desaturate your sheet of plasma.

Do Filters>Blur>Gaussian Blur and blur it by about 18-25 pixels.

Do Filters>Edge Detect>Edge. Set it to Sobel and max out the value.

You won't see much at this point, just some shadowy, blurry forms against a black background.

Now do Colors>Threshold. In the window that pops up, you will see a sort of "hump" at the left end of the histogram window. Move the left slider left to about the middle of this hump. Move the right slider left until it is at least at the "foot" of the hump and perhaps a bit more. Click OK.

Now Gaussian Blur the layer again by the same amount you did before.

Run Edge Detect again, only this time, you will want to lower the value until the highlights aren't quite so blown out. I use a value somewhere in the rage of about 3-5.

This will give you sort of "medium" worms.

To get "finer" worms, run Edge Detect again, but set the value lower so that the highlights don't blow out too much, probably 1-3.

Now run Gaussian Blur again, but set the value to about half what you have used before.

Run Edge Detect again with the same value. Now you will have a "finer" batch of worms.

This technique also works with solid noise with just slightly different results.