So Richard Feynman wrote about how one might store a complete set
of Encyclopedia Britannica on the head of a pin.
http://www.pa.msu.edu/~yang/RFeynman_plentySpace.pdf
And now someone's quoted him;
using individual atoms!
http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2016.131.html
Very nifty.
-Patrick
(the tech has been around for a while, they've figured out a way
to control a read-write head that can move over the surface and do
this)