Abstract: Gravitational waves are small changes to spacetime that are generated by the most violent events in the universe. The detection of merging black holes with masses up to ~100x the mass of the sun has become nearly commonplace at this point. But there are many more binary black hole systems out there, along with other novel and exotic gravitational-wave sources as well. The gravitational-wave background is the overall “hum” of gravitational-waves in our Universe, and it is the sum of all the sources we cannot detect individually. We search for this background using ground-based detectors like LIGO, Virgo, and KAGRA in the 10-1000 Hz frequency band, and I will discuss those search efforts, challenges they face, and what we could learn from a detection in the future. Recently, pulsar timing array experiments reported evidence for a gravitational-wave background with frequencies ~nano-Hertz that is consistent with a population of supermassive binary black holes. I will discuss the implications of this result, outline how the experiment works, and discuss some of the novel statistical methods we used to perform that search. Along the way, I’ll highlight similarities between the GW background searches at such different frequency scales.