Chemical and physical properties of pre-stellar cores

Pre-stellar cores are the preferred location for the formation of Sun-like stars. These dense and cold fragments of molecular clouds represent the initial conditions for the assembly of stellar systems. Furthermore, there is growing evidence that also the chemical composition of evolved systems is at least partially inherited from the pre-stellar stages. The study of these objects is, therefore, crucial to understanding the subsequent planetary formation. Since they are short-lived, however, they are fairly rare. In this talk, I will present the most recent results in terms of the chemical compositions of nearby, pre-stellar sources, and I will show our recent efforts in trying to expand the sample of these objects to perform statistical studies. Moreover, since the analysis of molecular line emission unveils important information also on the physical properties, I will illustrate a few examples in these regards. In particular, I will focus on the importance and recent measurements of the ionisation rate due to cosmic rays in dense gas, and its dynamical implications.