Cheese fungus. Coloured scanning electron micrograph (SEM) of Penicillium fungus used in cheese manufacture. Conidiophores (fruiting structure) and conidia (asexual spores) form at the tips of specialized hyphae. Penicillium is used as a starter culture for blue-veined cheeses, being responsible for their flavour and colour. It is also a common spoilage organism in various foods. Magnification: x1600 when printed at 10 centimetres wide.