A container assembly with improved mixing dynamics for mixing substances in preparation for injection by an injection device or for the dispersion of additives in the collection and analysis of biological samples is disclosed. In one configuration, the container assembly includes a first mixing element protruding into an interior of a container. With the container rotated about its longitudinal axis, the first mixing element forms at least one vortex which effectuates mixing of a first substance provided within the container interior and a second substance provided within the container interior.
