Laser spectroscopy of cold molecules is a powerful tool to address fundamental physical questions. We develop new methods to cool and control neutral molecules and apply them to improve the resolution of the spectroscopic measurements. In particular we exploit the Stark energy of polar molecules in non-homogeneous electric fields and use both conventional and microstructured devices to decelerate and trap cold molecules. Further, we develop novel narrow-linewidth light sources in the mid IR which are absolutely referenced to the primary frequency standard via a fibre-link to the National Metrological Institute in Torino, INRIM.