Stair of the Week is an alternating tread storage stair
Dezeen shows this alternating tread stair designed by Schemaa, in a "micro-apartment" in Paris. The bed is in a loft accessible by the stair; all of the space below is used for storage.
Alternating tread stairs usually use up a lot less space than conventional ones, and are safe and comfortable once you get used to the fact that you have to lift your feet in the right order. In previous discussions about them, owners have suggested that handrails are nice to have as it is a bit different than conventional stairs. I suspect the handrail police will complain.
But hey, we know what architects think about handrails. They just clog up the clean lines.
There's a lot more going on in this cute little apartment; lots more photos in Dezeen.