This text aims at highlighting a typology of small firms which, beyond those resting upon size or industry, allows to distinguish the firms according to their internal organization and the type of market on which they act. We will thus try to arrange the population of SMEs which is still often considered as an homogenous subset of the national productive system and to make emerge some so-called "worlds of production," referring to the Salais and Storper terminology. Using a Hierarchical Ascendant Classification method applied to a sample of SME we succeeded in highlighting an economic diversity in this population. Thanks to the location of the various groups of explicative factors of the positioning of a firm in a world of production and of its own situation compared to the other firms belonging to the same world, we show that the nature and the quality of the firm are largely determined by the couple (goods, market) which characterizes it.