Despite the complexity of the topic, Princeton University professor Stephen Gubser offers a succinct, accessible, and entertaining introduction to one of the most debated areas of physics today. Black holes are real objects, not just a thought experiment! Black holes are extremely convenient from a theoretical point of view, since they are mathematically much simpler than most astrophysical objects, such as stars. Things get weird when it turns out that black holes aren't really that black after all. What's really inside them? How can you imagine falling into a black hole? Or maybe we are already falling into it and just don’t know about it yet?