(box|bag) in (box|bag) in (box|bag)
It's easy enough to put containers in containers if the containers are the same but just smaller: matroyshka dolls, nested suitcases, plastic bags underneath the sink. I respect the fans of homogenous container nesting but I contend beauty arises in contrast.
It's also easy enough to put containers in containers with a single layer of recursion. I believe true greatness in nested containerization begins at the three layer stage.
Let us define a box as a hard container and a bag as a soft one. Join me in a pathologically deranged exploration of three members of (box|bag) in (box|bag) in (box|bag).
Box in Box in Box: Elevator
Recognizing elevator in a building as box in box is trivial. Where is the third? A building is the outer box, the elevator is the inner. As we step across the sill of the elevator door we are also stepping into a single entrance of the elevator shaft, a simultaneous entry into the inner box in box.
The core conceit of this specific construct is locomotion within a hidden interstitial box.
An elevator on a cruise ship is a locomoting box within a box within a locomoting box.
Theoretically a missile inside a fighter jet inside an aircraft carrier is a locomoting box within a locomoting box within a locomoting box. To me this is unaesthetic on multiple fronts: neither the fighter jet nor the missile substantially locomote while still inside the carrier, and only the aircraft carrier has vestigial traces of a canonical rectangular box.
Box in Box in Bag: Encased Phone in Pocket
Is a phone a box? A phone is rectangular prism, into which components are placed. Does the interior of a box need to be functionally accessible? In the time when phones had battery compartments, they were definitely boxes. Modern phones are so densely packed and difficult to open that they veer more towards slab than box.
Is a phone case a box? Structurally, it is hard with defined rectangular geometry. What makes me uncomfortable is that despite having only one open face, the open face is perpendicular to the smallest rectangular dimension and thus occupies nearly half the box's surface area. Moreover it is a box that fits exactly one thing perfectly, with no margin, and a flexibility unbecoming of the category. If a case is a box, is a shoe a bag?
Is a pocket a bag? I believe a bag does not need to be sealed or sealable, as the containment of a bag is derived from its material conformity. However a pocket does not have an independent existence. We would expect a bag can be picked up and moved. Perhaps a pocket is a vestigial bag.
Overall, a quite liminal member of box in box in bag.
Bag in Box in Box: Refrigerated Bagged Milk
Canadians, for reasons we shall not explore here, purchase milk in plastic bags (usually packaged in groups of 4 in plastic bags themselves).
These bags are placed by the Canadian into what amounts to a plastic pitcher without a spout. Usually this plastic pitcher has an integrated mini milk bag cutter, for slicing open a corner of the bag before the complex is placed inside a refrigerator shelf.
I have already previously argued that a phone case is a box despite being open on one of its faces. Therefore I propose that this pitcher is also a box, being enclosed on all sides except one.
It would of course be more convenient to slice open the bag and simply pour the milk into an ordinary pitcher. But then a layer of nesting would be lost, and so Canadians have invented a box to hold a bag of milk to treat it like a box of milk.