In my dissertation, I have analysed the ammonia observations and the derived physical parameters of 36 Planck Galactic Cold Clumps, to search for systematic correlations between the calculated densities (NH3 column density, H2 volume density) and temperatures (excitation, rotation and kinetic temperatures) in the gas. The comparison of these parameters may imply the evolutionary state of these objects and reveal the differences and common signatures in the star formation process in different environments.