Massive Stars: Key to Solving the Cosmic Puzzle
  We describe observations in the nearby universe (<100 Mpc) with a 10-m or
larger space-based telescope having imaging and spectral capabilities in the
range 912-9000 \AA that would enable advances in the fields of massive stars,
young populations, and star-forming galaxies, that are essential for achieving
the Cosmic Origins Program objectives i) how are the chemical elements
distributed in galaxies and dispersed in the circumgalactic and intergalactic
medium; and ii) when did the first stars in the universe form, and how did they
influence their environments. We stress the importance of observing hundreds of
massive stars and their descendants individually, which will make it possible
to separate the many competing factors that influence the observed properties
of these systems (mass, composition, convection, mass-loss, rotation rate,
binarity, magnetic fields, and cluster mass).
