Species of "Penicillium" are ubiquitous soil fungi preferring cool and moderate climates, commonly present wherever organic material is available. Saprophytic species of "Penicillium" and "Aspergillus" are among the best-known representatives of the Eurotiales. They live mainly on organic biodegradable substances. Commonly known as moulds, they are among the main causes of food spoilage. Many species produce toxins which work against bacteria and other fungi. The ability of these "Penicillium" species to grow on seeds and other stored foods depends on their ability to thrive in low humidity and to colonize rapidly by aerial dispersion while the seeds are sufficiently moist. Some species have a blue colour, commonly growing on old bread and giving it a blue fuzzy texture.