During the last years a new economic theory to address business problems has been strengthening. The analysis of the several different theoretical approaches of the firm indicate that transaction complexity inside the company and the indetermination inherent to unbalance in repeated interaction between the firms cast doubt both about traditional models and their outcomes. The work specially emphasizes the fact that the companies are institutions, with a category tantamount to that of the market. In this regard, the paper looks into the new theory of the firm and the relation existing between the several different approaches. Along the theoretical dimension the newest breakthroughs in this field are analyzed and the link between game theory, information economy, contract theory, modeling and the different manner to perform empirical application is explained.