Packaging for packaging a product such as a cosmetic composition

A package (100) for packaging a product, comprising:

• a container (1) provided with an opening (10) and defining a housing (11);
• a lid (3) that is movable between an open position and a closed position, the lid closing the opening (10) of the container (2), when in the closed position;
• and
• a storage unit (2), the storage unit comprising:
• a vessel (21), housed at least partly in the housing (11) of the container (1) and defining a reservoir (20) suitable for receiving the product, said vessel being movable along a vertical axial direction (Z) between a rest position, a raised position, and a lowered position, and
• a pressure difference compensation system (22) that is elastically deformable and suitable for forming a sealed connection between the vessel (21) and the lid (3),
• wherein the storage unit (2) defines, in combination with the lid (3) in the closed position and for a constant amount of the product, a sealed compartment (8) having a first volume (V1) when the vessel (21) is in the rest position, a second volume (V2) less than the first volume (V1) when the vessel (21) is in the raised position, and a third volume (V3) greater than the first volume (V1) when the vessel (21) is in the lowered position, and
• wherein, in the closed position of the lid (3), the vessel (21) of the storage unit (2) is in the rest position when a pressure (P1) inside the compartment (8) is equal to a pressure (P2) outside the package (100), is in the raised position when the pressure (P1) inside the compartment is less than the pressure (P2) outside the package, and is in the lowered position when the pressure (P1) inside the compartment is greater than the pressure (P2) outside the package.