It's not just the uber-rich freezing their brains and bodies when they die. An HBO show visited a conference filled with everyday people excited to do it.

• The series finale of HBO's "How To with John Wilson" explored cryonics and the quest for immortality.
• The topic has drawn the attention of the ultra-wealthy in recent years.
• Sam Altman, Jeff Bezos, Peter Thiel, and Bryan Johnson all invested in anti-aging or cryonics.

HBO's idiosyncratic docuseries "How To with John Wilson" recently aired its final episode, exploring — rather fittingly for the ending of a show — the topic of cryopreservation, or freezing one's brain or body upon death. It's a subject, along with immortality and eternal youth, that many people seem to be occupied with, especially Silicon Valley's ultra-wealthy.