The aim of this work is to introduce and to put closer ways how microflora that surrounds us is changing the composition and contaminating food that we need in it's healthy and unaltered form as well as the types of germs that cause food spoilage or act as pathogens that cause the various diseases in humans and animals. Also, this work contains a description of the ways in order how to prevent contamination to acceptable values, that is, those that can not harm human health. Certainly the origin of microbes in or on various commodities varies depending on the internal and external parameters that affect their growth, survival, and death in foods and the conditions in which the food is grown or kept and the same goes for te products obtained from raw foods. Procedures to preserve foods can include deep freezing, dehydrating, cooking, pasteurization or sterilization or using a hypotonic saturated with sugar, which preserve food and provide for it's long standing. In each of the above processes, it is extremly important the hygiene of workers, working tools, but also the space in which the food is processed or stored. In therms of modified atmosphere where low humidity is used (depending on the type of foods - fruits, vegetables), and carbon dioxide, it is extremely important to maintain the conditions within certain limits so as to avoid the development and growth of the microbal population. Furthermore, agents of food spoilage as well as pathogens have bbe appointed as tabular representation of description thereof, depending on the type of foods that become contaminated. Some of the most important and frequent microbes that cause food spoilage and / or acting pathogens, are described in more detail in the reminder of this work and are also presented with the illustrations.