It really seems, like Richard Feynman said in one of its famous lecturers, that there is plenty of room at the bottom.
Scientists at Delft University have managed to use a single atom to store a bit, or better, a structure where the presence of an atom or the missing of an atom can be used to store the 1 or 0 value.
At this level of storage one can store 500TB per square inch. Till 2015 the highest storage density achieved was through magnetic media was 1.3TB per square inch and in February 2016 for the first time NAND memory (based on silicon) achieved a higher density reaching 3TB per square inch. Well, what the scientists at Delft did was to increase this density 150 times!
To write the bits on single atoms the scientist used a scanning tunneling microscope (STM) that works like a nano needle that can push the atoms around. It is not the first time that an STM is used to move atoms, actually the first published occurrence was back in 1989 when IBM researchers wrote the word "IBM" using and STM to push xenon atoms on a nichel substrata.
The Delft scientists used chlorine atoms on a copper substrata and have found a more effective way to move atoms around. They demonstrated the capability of their system, and its (relative) scalability by creating an 1kB memory by assembling blocks of 8 bytes each. And guess what? They wrote on that memory Richard Feynman's lecture "There is plenty of room at the bottom".
It is an amazing achievement, but do not expect to see this kind of atomic storage becoming available, nor in this decade nor in the next one.