What type of stem cell has the capability to form an entire organism?

Totipotent stem cells have the unique capability to form an entire organism. These cells can differentiate into all cell types necessary for development, including both embryonic and extraembryonic tissues, such as the placenta. This characteristic is established in the earliest stages of development, where a zygote or early embryo consists of totipotent cells that can give rise to every cell type required for a full organism.

In contrast, pluripotent stem cells can develop into nearly any cell type but are limited to forming tissues within the organism itself and cannot contribute to extraembryonic structures. Multiple potent and oligopotent stem cells have even more restricted differentiation capabilities, typically limited to specific cell lineages or a few types of cells. Thus, the unique ability of totipotent stem cells to contribute to all aspects of an organism's development distinguishes them clearly from the other types listed.