What is best to use as storage for breastmilk? Storage bags, trays or cups?

I believe most pumping moms who go to work use disposable storage bags. If you want to keep a bigger stash, you may want to use one as it doesn't take up so much space in the fridge. I just use storage cups, too. Looney Tunes and Bebeta are a few of the cheapest but quality brands that I know of