Container assembly (500) comprising a container (1) for storing a tissue sample(45) and a cover (2) adapted to engage with the container (1). The cover (2) comprises: a top member (321) comprising a receptacle (211), a seal (22) for sealing off said receptacle (211),a puncturing member (323) for breaking said seal (22) by displacement of the puncturing member (323).The container assembly (500) has a first and a second position, wherein in the first position the container (1) is isolated from the receptacle (211), and in the second position fluid communication is provided between the receptacle (211) and the container (1). The container assembly (500) comprises a separator (31) positioned between the seal (22) and the bottom (13) of the container (1), and the separator (31) is provided with at least one aperture adapted to provide a fluid passage between the receptacle (211) and the container (1).
