by Brady Haran

Now, there are "nano test tubes" so small they hold just a few hundred atoms.

Such containers, with a diameter equivalent to about 20 atoms, have been manufactured by experts at the University of Nottingham.

In a paper published in the latest issue of science journal Nature, the scientists explain how it was done.

HOW IS IT DONE?

Chemists started the process by manufacturing two chemicals: melamine and a derivative of perylene.

Dr Neil Champness said: "These molecules are very specifically designed such that when you put them together they will organise themselves into a honeycomb-type structure.

"The honeycomb we make contains lots of small pockets, or what could be termed containers, within the overall arrangement.

"These containers are about 20 atoms across and in total would only contain a few hundred atoms."

The physicist working on the project, Professor Peter Beton, said: "This is analogous in the everyday world to emptying a pile of bricks on to the ground which then, instead of forming an unstructured heap, spontaneously arrange themselves into an ordered structure, for example, a wall or block paving."

As part of the experiment, the scientists filled each container with large molecules known as buckyballs, a form of carbon.

But what good are containers that are so small they can only be detected with a high-tech scanning tunnelling microscope?

Dr Champness said: "Nanotechnology is all about using molecules and atoms for a very specific purpose, such as things like molecular-based computing.

"Of course if you want to do something on that scale, you need somewhere to put your molecules, and that is what we are managing to achieve."

BBC News Online, East Midlands