Abstract: Although most of the stars in the Milky Way, including the Sun, are born in stellar clusters, the details of the cluster formation process are still not fully understood. It is well-known that it must be intimately related to the fragmentation process of molecular clouds, but a number of cloud properties such as density and temperature structure, turbulence, stellar feedback, initial angular momentum, and magnetic fields could influence this fragmentation process. In this talk I will present several observational campaigns aimed at exploring potential relations between cloud properties and their fragmentation level, with a special emphasis on the role of the magnetic field. In addition, the formation of the lowest mass members of the clusters, i.e., brown dwarfs and free-floating planets, is also a matter of intense debates, with the star-like and the planet-like scenarios being the most promising. I will show some of the observational efforts done so far to constrain the theories of formation of the lowest mass members. Finally I will show preliminary results of a blind search of complex organic molecules in one of the clouds of our sample with highest fragmentation, which suggests that these molecules might be more common than previously thought, including the substellar regime.