The tetraploid complementation assay is a scientific technique used to evaluate the ability of embryonic stem cells to contribute to the development of a living organism. It involves combining two sets of cells - one that lacks the ability to form a complete organism on its own and another that can provide the necessary genetic material to form a viable organism. The term "tetraploid complementation assay" may be referred to as "ploidy complementation assay," "embryonic stem cell complementation assay," or simply "rescue assay." All of these terms describe the same scientific technique used to study embryonic stem cells and their potential in development.