My dear aunt used to crochet with floss as fine as spider web. She made beautiful things, from doilies to bedspreads. The thread was just too fine for me to work with.
What lovely colors. I was able to crochet a few things using thread like this but it was never my favorite. Too small and took such good eyesight. Seemed to take forever to complete a project!
I'm thinking it might be used for embroidery???