The most powerful objects in the universe are growing giant black holes that inhabit the centers of galaxies and play an important role in their development. This project undertakes the analysis of new and archival telescopic observations to improve our ability to measure the masses of these objects and to better understand the role that giant black holes play in our universe. Research opportunities for undergraduates are provided in the project as is a workshop for science writers. The investigation is based on long-duration and high-fidelity monitoring of about 100 luminous active galaxies mainly using the Wyoming Infrared Observatory. The technique, called reverberation mapping (RM), is arguably the best way to determine the mass of black holes powering nuclear activity in galaxies. RM relies on time-domain spectroscopy to measure the size and speed of gas in the gravitational influence of the giant black holes which together provide a mass measurement. Scaling relationships based on RM results have been used to generate nuclear black hole mass estimates of hundreds of thousands of active galaxies, which in turn have been used for many projects in astronomy. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.