Gravitational waves were predicted 100 years ago by Einstein as part of his general theory of relativity. This volume contains the exciting results presented at IAU Symposium 338, following the announcement of the first results of the observation of the collision of neutron stars by the LIGO and Virgo Advanced detectors, and follow-up observations by many ground-based and space telescopes. These observations provided an incredible context for the talks, posters and discussions at the meeting, fostering new interactions and collaborations between physicists and astronomers in an exciting new era of multimessenger astrophysics. For the first time, space-time messengers (gravitational waves) and electromagnetic ones (visible, infrared and ultraviolet light, x-rays, gamma-rays, radio waves) can be correlated, to increase our understanding of binary systems of compact objects, rotating or exploding stars and other astrophysical phenomena. A new window has opened through which we can view the cosmos.