An apparatus and associated methods of use for a controlled combination of reagents is disclosed. The apparatus includes a vessel 400, a vessel insert 220, and a cap element 200. The vessel 400 has a body portion 410 for receiving a biological sample. The vessel insert 220 receives at least one reagent therein. Preferably, the vessel insert 220 is received in a portion 420 of the vessel 400. The cap element 200 is attached to the vessel 400 to secure the vessel insert 220 in the vessel 400. During use, the vessel insert 220 is adapted to release its contents when the biological sample is introduced into the body portion 410 of the vessel 400 upon application of an intermixing force to the vessel insert 220. A variety of intermixing forces may be applied, depending upon the embodiment of the present invention and its associated methods of use.
