False-colour transmission electron micrograph (TEM) of a single Bacillus subtilis bacterium (termed the Hay Bacillus). This species of aerobic rod-shaped Gram-positive bacteria is seen at the end of a process of spore formation (sporulation). At lower centre, it has developed an endospore with many membranes (red, green) forming a thick protective coat. This is a resting phase induced by adverse conditions, & the spore will germinate when conditions become favourable. B. subtilis is sometimes pathogenic on humans: causing severe eye infections (iridocyclitis or panopthalmitis). Magnification: x860 at 6x7cm size.