In the early days of computers, a hard drive with a few megabytes was an unimaginable amount of storage. Then we hit 100 megabytes, then a gigabyte, then a terabyte, and sizes are still increasing rapidly with a 10 terabyte hard drive arriving earlier this summer.
However, at some point we will hit a wall as existing magnetic storage technology gets shrunk as far as it can go. Solid-state memory can carry us a bit further thanks to 3-D stacking techniques, but even that's not as good as it gets. There's a natural solution that can do much better.
That solution is DNA. Yes, the double-helix building-block of life that tells your body what to do could be the ultimate future hard drive.
DNA stores information in combinations of four base pairs, which wouldn't be hard to adapt to our existing binary system. In fact, researchers have already done it, both for writing and reading information.