Freeze-etching of never-dried pellicles or of incubated suspensions of both Acetobacter xylinum and Acetobacter acetigenum show a nascent form of the cellulose microfibril which has a core surrounded by an amorphous sheath. Drying of the pellicle or suspension reduces the diameter of the sheath and changes the form of the microfibril to the one usually seen. This nascent form of the cellulose microfibril is consistent with previous postulations of an intermediate polymer or polymers in the biosynthesis of cellulose.