Earlier this year, a couple of scientists in a laboratory did something incredible. Using nothing but the genetic code and a well-equipped lab, they raised the dead.  Specifically, the extinct horsepox virus was brought back to life. The scientists said that they didn't do the experiment out of any malice for horses, but just to demonstrate that - with a few good biotech experts, a decent lab, and $100,000 - anyone would soon be able to bring viruses back from the dead. So what about when that virus is smallpox, capable of killing millions, with the only surviving samples stored as bioweapons by the US and the Russians? Could it be that the biotech revolution - which has such power to save us from our ills and woes - might doom us as well? And what happens when this power gets into the hands of more and more people; the power over life and death?  As ever, you can follow us on Twitter @physicspod, where we're amazingly active and will respond to any queries you have about the end of the world and similar terrors. You can tell us what you think of the ranking so far, make your own suggestions, and even donate to the show if you like. If you've enjoyed it, please consider rating and reviewing the show on iTunes, which helps us get noticed!