Recent developments in the field of cell therapy and regenerative medicine describe mesenchymal stem cells (MSCs) as potential biological products due to their ability to self-renew and differentiate. MSCs are multipotent cells with immunomodulatory and regenerative properties. Because of their therapeutic potential, they are extensively studied to assess their viability, safety and efficacy. This chapter describes the main characteristics and sources of MSC cells, as well as their properties and current clinical applications. It also presents the latest information on the regulatory aspects that define them as somatic cell therapy medicinal products. MSC-based cell therapy is currently offered as a pharmacological alternative, although we still face many challenges in this area.