AMAC Plastic Box
Sleek, simple and stackable, the AMAC plastic boxes have been in production for over 50 years since Gene Hurwitt introduced them to the pharmaceutical industry. They were soon adapted by Andy Warhol and today are a part of MoMA's permanent design collection.
AMAC themselves put it quite perfectly:
An elegant expression of modernist simplicity, stripped of adornment, and almost invisible except for its utility.
The iconic boxes come traditionally in transparent plastic, but the brightly colored opaque set is my personal favorite!