Unraveling the Structure of Molecular Clouds in the Milky Way and Beyond

	Molecular clouds are the sites where stars and their planets form. It is essential that we develop a  detailed understanding of the structure of molecular clouds if we wish to understand the cosmic star formation history as well as the birth of alien Earths. New instruments like ALMA now allow to make great leaps forward toward this goal. Research into high-mass star formation has in particular benefited from new observations. High-resolution data from interferometers now revolutionize our views on the fragmentation of clouds into star-forming cores. Further, astrochemistry helps to identify the coldest and densest structures near the onset of star formation. In combination this work has now led to the realization that star formation does not necessarily adhere to a few simple rules, like those put forward by Larson three decades ago. Clouds greatly differ in their gravitational binding, and magnetic fields appear to play a much more important role than thought previously. A diverse zoo of molecular clouds populates the Milky Way.  This zoo becomes even more diverse when considering clouds within a few 100pc from the Galactic Center. New observations from ALMA and other interferometers of the Central Molecular Zone (CMZ) reveal that CMZ molecular clouds are exceptionally dense and massive --- but for some strange reason these clouds are largely devoid of star formation. This observation might have important implications for the interpretation starburst galaxies that are populated with molecular clouds that have densities similar to those of CMZ clouds.