Yeast (specifically Saccharomyces) is a well-known exception in the fungal kingdom because it is unicellular and does not possess a true mycelium or hyphae. While most fungi are multicellular and organized into thread-like structures called hyphae, yeast typically exists as single cells that reproduce by budding. Under certain rapid growth conditions, they may form chains of cells called "pseudohyphae," but these are not true hyphae.

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