sentences:  The first image shows only one "snapshot" of what a particular mediator complex might be composed of, but it certainly does not accurately depict the conformation of the complex "in vivo".During evolution, mediator has become more complex.The yeast "Saccharomyces cerevisiae" (a simple eukaryote) is thought to have up to 21 subunits in the core mediator (exclusive of the CDK module), while mammals have up to 26.