Abstract: In a packaging unit comprising a container, a flexible closure mounted thereto and at least one compartment located underneath the closure within the container. The compartment is adapted to release its content in the container when the closure is peeled sufficiently therefrom. The container and the compartment are made of plastics materials whereas the flexible closure is made preferably of aluminum foil. In one embodiment, the compartment comprises frangible sections along its sidewall and its bottom wall whereby removal of the closure causes rupture of the compartment at its frangible sections thereby releasing the content of the compartment into the content of the container. In a further embodiment, the flange which extends peripheral outwards from the upper ends of the sidewalls of the compartment is heat-sealed in one section thereby completely to the closure and in another section thereof only partly thereto.