Planck has observed the entire sky from 30 GHz to 857GHz. The observed foreground emission contains contributions from different phases of the interstellar medium (ISM). I will present an all-sky map of the apparent temperature and optical depth of thermal dust emission using the Planck-HFI (350 µm to 2 mm) and IRAS (100 µm) data. The optical depth maps are correlated to tracers of the atomic (HI) and molecular gas traced by CO, which unveils excess dust emission which has been attributed to thermal emission by dust associated with a dark gas phase. Further, I will show how we have separated the observed Galactic emission into the different gaseous components (atomic, molecular, ionised and dark gas) as well as into a number of Galactocentric rings. This technique provides the necessary information to study dust properties (emissivity, temperature, etc.), as well as other emission mechanisms as a function of Galactic radius. I will present explore contribution of various emission mechanisms to the Planck signal. Apart from the thermal dust and free-free emission, the Galaxy has been probed for anomalous (e.g., spinning) dust as well as synchrotron emission.