The proceedings of IAU S321 summarize our understanding of the rarefied universe. They discuss the most recent advances in studies of the stellar, dust and gas content of galaxy outskirts, going from resolved stellar populations in the Milky Way and in the Local Group out to high-redshift systems.
The proceedings of IAU S321 summarizes our understanding of the rarefied universe bordering galaxies from the Milky Way out to high-redshift systems.