A container assembly for storing a biological sample, said assembly comprising: a container having a bottom, a side and an open top end, said container having a dimension to contain a volume of a reagent sufficient to treat a biological sample; a closure cap (14; 150) for coupling to said open top end of said container; and a sample holder (16; 152) including a side wall (72, 174) and coupled to said cap and being positioned to be received in said container, said sample holder having an internal cavity (84; 194) with a dimension for receiving a biological sample, said holder having a plurality of fluid openings (74; 176) into said cavity to enable free flow of said reagent into said cavity while retaining said biological sample in said cavity, said sample holder having a dimension to fit between said bottom and side of said container and said cap and to immerse said cavity in said reagent, said cavity of said sample holder having a volume to limit the size of said biological sample to maintain a predetermined ratio of an amount of said biological sample to an amount of said reagent to treat said biological sample, characterized in that the sample holder (16; 152) has an open bottom end (78; 196) and a top end at which a top wall is coupled to said side wall (72, 174), said closure cap closes said open top end of said container; and said open bottom end being provided with a closure member (108; 198) for closing said open bottom end, said closure member being pivotable from said open bottom end, wherein said closure member is coupled to said sample holder and is pivotable about an axis oriented in a plane parallel to a plane of said side wall. a container having a bottom, a side and an open top end, said container having a dimension to contain a volume of a reagent sufficient to treat a biological sample; a closure cap (14; 150) for coupling to said open top end of said container; and a sample holder (16; 152) including a side wall (72, 174) and coupled to said cap and being positioned to be received in said container, said sample holder having an internal cavity (84; 194) with a dimension for receiving a biological sample, said holder having a plurality of fluid openings (74; 176) into said cavity to enable free flow of said reagent into said cavity while retaining said biological sample in said cavity, said sample holder having a dimension to fit between said bottom and side of said container and said cap and to immerse said cavity in said reagent, said cavity of said sample holder having a volume to limit the size of said biological sample to maintain a predetermined ratio of an amount of said biological sample to an amount of said reagent to treat said biological sample, characterized in that the sample holder (16; 152) has an open bottom end (78; 196) and a top end at which a top wall is coupled to said side wall (72, 174), said closure cap closes said open top end of said container; and said open bottom end being provided with a closure member (108; 198) for closing said open bottom end, said closure member being pivotable from said open bottom end, wherein said closure member is coupled to said sample holder and is pivotable about an axis oriented in a plane parallel to a plane of said side wall.