Our perception of the universe has changed dramatically from thoughts of a starry, unknown realm to knowledge of the countless galaxies that surround us, yet the scale of the cosmos remains a mystery. How old is the universe? How much matter and energy does the universe contain? 21st Century Cosmos probes questions of cosmology with international astronomers to refine our understanding of how stars and galaxies are formed, if the universe is flat or curved, and how and why the universe will continue to expand.