yeast cell

one cell of yeast, one living yeast organism

Yeasts are a growth form of eukaryotic microorganisms classified in the kingdom Fungi, with approximately 1,500 species described. Most reproduce asexually by budding, although a few do by binary fission. Yeasts are unicellular, although some species with yeast forms may become multicellular through the formation of a string of connected budding cells known as pseudohyphae, or true hyphae as seen in most molds. Yeast size can vary greatly depending on the species, typically measuring 3–4 µm in diameter, although some yeasts can reach over 40 µm.
See more at Wikipedia.org...