High-Mass Star and Massive Cluster Formation in the Milky Way
  This review examines the state-of-the-art knowledge of high-mass star and
massive cluster formation, gained from ambitious observational surveys, which
acknowledge the multi-scale characteristics of these processes. After a brief
overview of theoretical models and main open issues, we present observational
searches for the evolutionary phases of high-mass star formation, first among
high-luminosity sources and more recently among young massive protostars and
the elusive high-mass prestellar cores. We then introduce the most likely
evolutionary scenario for high-mass star formation, which emphasizes the link
of high-mass star formation to massive cloud and cluster formation. Finally, we
introduce the first attempts to search for variations of the star formation
activity and cluster formation in molecular cloud complexes, in the most
extreme star-forming sites, and across the Milky Way. The combination of
Galactic plane surveys and high-angular resolution images with submillimeter
facilities such as Atacama Large Millimeter Array (ALMA) are prerequisites to
make significant progresses in the forthcoming decade.
