Why is it necessary to speak about soil? This lecture was given by Mr. Boubaker Houmène on the occasion of the International Year of Soils and outlined the importance of soil science. Soil, as the epidermis of Earth, is an organized system of production. It comprises wells and sources of greenhouse gases. It is a real regulator of hydrologic cycle and a real scrubber environment of pesticides, heavy metals and others. Soil is a living environment which is considered to be a real reserve of microorganisms necessary for organic degradation into simple chemical components used by plants.