It's hard to imagine living for 100 years or more, but then our ancestors could scarcely imagine a world in which few people died as children. Fatal childhood diseases are now rare in developed countries.
And science is always looking at the other end of life. Science journalist Chip Walter takes a look at the effort going into extending human life, and the gobs of money funding that effort.
Walter's book is Immortality, Inc.: Renegade Science, Silicon Valley Billions, and the Quest to Live Forever. Are we getting closer to people routinely living to the century mark? We explore with the author.