Religion. There are so many belief systems in the world, it's obviously a vital part of human existence. If religion didn't exist, we would have to invent it.
The ascent and (ongoing) descent of H. sapiens. I find it extremely interesting, if not distressing, how, as the Alpha life form on this planet, our species could mess things up so abysmally, both for own species and the rest of life on Earth.
Right now I'd say stories of folks who have had near death experiences. Folks who are on their death bed, very calm and seeing friends or relatives who have already passed away. Things like that..