Researchers in the Netherlands have unveiled the world's smallest hard disk.

The disk uses chlorine atoms to represent each bit of information, the most efficient data storage method yet devised. The hard disk stores 1 kilobyte of data, or 8,000 bits, and features a storage density of 500 Terabits per square inch -- 500 times better than the most efficient hard desk on the market.

"In theory, this storage density would allow all books ever created by humans to be written on a single post stamp," lead researcher Sander Otte, a scientist with the Kavli Institute of Nanoscience at Delft University, said in a news release.

Researchers used a scanning tunneling microscope to manipulate atoms to represent binary code, the language used to encode data in computers.

"Every bit consists of two positions on a surface of copper atoms, and one chlorine atom that we can slide back and forth between these two positions," Otte explained. "If the chlorine atom is in the top position, there is a hole beneath it -- we call this a 1. If the hole is in the top position and the chlorine atom is therefore on the bottom, then the bit is a 0."

Using the scanning tunneling microscope, scientists can drag holes around on a copper surface to encode all kinds of information. Researchers liken the hard disk to a sliding puzzle, where each piece is either an atom or a hole.

Because each chlorine in atom is surrounded by other chlorine atoms, they remain stable and stationary. Previous attempts to encode data on the atomic scale have relied on loose, unanchored atoms.

The data on the hard disk is organized into blocks of 8 bytes, or 64 bits. Each block has a marker made of holes that works like a bar code, revealing the location of of the block on the copper layer.

The new method promises major improvements in terms of stability and scalability, but the technology requires significant improvement before it can be used in a working datacenter.

"In its current form the memory can operate only in very clean vacuum conditions and at liquid nitrogen temperature, 77 Kelvins, so the actual storage of data on an atomic scale is still some way off," Otte said. "But through this achievement we have certainly come a big step closer."