SNAPWARE CONTAINERS! They come in sets of two, with one lid. Each compartment acts as the other's lid. So you could technically stack lots and lots! However, when filled with nail polish (which makes them quite heavy), it is definitely NOT a good idea to lift these by the handles if you have to move them. But it's no big deal. They're awesome, so I can get past that one flaw. Which isn't technically a flaw, as I don't think they're actually made for storing nail polish... ANYWAY, that's beside the point. Did I mention they're awesome??They're the perfect depth for typical nail polish bottles. The only ones that cause a bit of trouble are the Sephora by O.P.I brand. They're a little tall, so you'll have to store those on the very top compartment. The blue lid fits perfectly on top of them, but another section will not stack on top of that particular brand. Check out the picture below to see what I'm talking about. The Sephora by O.P.I colors are in the back left.
See how they're a bit taller?? No biggie. Just store them inside the top container and you're good to go. I also love how you can easily find the color you need by looking into the containers. No digging. I love it.
When you're done, they stack neatly out of the way under a bed, in a closet... wherever. 
They also sell smaller versions that come with three stacked containers that are great for storing nail files, clippers, cuticle balms, etc.
I was unable to find these on the Target website, but they sell them all sorts of places, and in actual Target stores if you are interested. Also, if you want to search for them online, the brand is Snapware and they're called "Snap-N-Stack" containers.
Check out my video below to see more about these containers and my nail polish organization and a peek at my nail polish collection.
xoxo- Tiffany