With the air, heat, moisture and the time which passes, the food are degraded. Very quickly, yeasts and bacteria appear. Only one bacterium can give some more than 33 million in twenty-four hours. Certain modes of conservation of food, like the drying of prunes to the sun, the marinade of anchovies in oil or the rolling up of cod in salt, go up with more than 400 000 years. Today, one more frequently resorts to preserve, deep freezing or pasteurization. Fred, Jamy and Sabine make us discover the universe of these micro-organisms which populate our food discreetly. They explain us the thousand manner of slowing down their proliferation.