I found a thin layer of fungus growing in my balsamic vinegar bottle.what went wrong?

Is the thin layer you are seeing on top of the liquid vinegar or at the bottom?

Mother has that name because it can 'make babies.' If you're checking into it, you can find directions.

What you probably see is your vinegar's "mother". If it is a mother, it's totally harmless. Filter it out with a coffee filter or consume it as many choose to do. Of course, as with anything on the Internet, don't take my word for it. Check your sources carefully and remember - test, test, and retest. I've included an image of an apple cider vinegar's mother for comparison as the balsamic vinegar is so dark it doesn't show very well. Good luck!

This is quite strange as vinegar can be used to kill fungus so for it to be growing in your bottle would mean that it has had something contaminate it. I hope it wasn't an expensive bottle!!!