Container assembly comprising: a container (1) configured to store tissue sample； said container (1) comprising: a bottom； a puncturing member (23) for breaking said seal (22) by displacement of said puncturing member (23)； a cover adapted to engage with said container (1), said cover comprising: a top member (21) comprising a receptacle (211), said receptacle (211) being adapted to contain a preserving agent, a seal (22) for sealing off said receptacle (211)； where the container assembly (100) 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), wherein the container assembly comprises a separator (31) positioned between the seal (22) and the bottom of the container (1).
