This work sheds light on certain aspects of interaction between employers and employees within the company, undertakes to analyze the decisions of each economic agent and highlights the role of human resources. It treats different issues related to the company's working environment, and consists of four works of applied microeconometrics. The first chapter deals with the dynamics of the exchange of aid between employees, in particular informal support networks. The second chapter focuses on the assessment of psycho-social risks in employees, its goal is to disentangle the ambiguous effects of...