Black holes are probably the most extraordinary objects in the cosmos: they can be born in violent explosions of very massive stars, they warp spacetime around them, they devour stars, and they generate gravitational waves detectable on Earth. We think that black holes of different sizes exist, from tiny and rapidly evaporating monsters to millions of solar masses in the centers of galaxies. Black holes continue to be at the edge of our knowledge; unraveling its mysteries is one of the most exciting challenges in human history, a challenge that will require all our capacities as a species and that will help us in our mission to understand the past, present, and future of this exciting place we call the cosmos.