This proposal comes to celebrate the act of posting via letter, where the written object will acquire, through its unfolding, the function of domestic object, that will at the same time become a memorial to the communication act made by someone close to us.
Aquarium is a C5 envelope, with a window and a plastic interior.

The envelope has a perforated all over which once is opened offers a great capacity as a water container because of its interior plastic concertina. After opened and filled up with water, the envelope gets transformed onto an aquarium.