Contribution Review talk
From clouds to dense cores
A large fraction of molecules have been observed in cold dark sources. These astronomical objects represent the starting point for the formation of molecules that will participate in the chemistry of the birth of stars and planets. They are also supposed to be the most simple objects in term of physical conditions and history. In this review talk, we will present a summary of the recent model developments that have been undertaken in the last 6 years to reproduce the chemistry in those regions and we will in particular discuss the importance of the formation of these sources and the history of the gas and dust under diffuse conditions.