The Cygnus X region is one of the richest star formation sites in the Galaxy, excited by the Cygnus OB2 cluster that contains well over 100 OB stars. Most of the molecular clouds are located at a distance of 1.4 kpc, the total molecular gas mass is a few 10⁶ M_⊙ and the average density is ~60 cm^-3. The northern region contains the prominent star-forming regions DR21 and W75N that are located within dense filamentary structures. The average UV-field is high (~300 G₀) and reaches peak values up to ~10⁵ G₀ in photodissociation regions (PDRs) close to Cyg OB2. The Cygnus X region is interesting to study because it shows many subsequent stages of star formation and –as a large complex –is the key to understanding the dominant role that massive star complexes play in external galaxies. The Cygnus X North region has a distinct filamentary structure that is exposed to a high overall radiation field, mostly arising from Cyg OB2, but also from many local HII regions.