Viewing nature
If you want to look at objects smaller than the naked eye can see, you need special instruments. Single lens magnifying glasses were invented about 1000 years ago, and spectacles in 1284, but credit for the first true microscope goes to two Dutch spectacle makers, Hans and Zaccharias Janssen. In the 1590s, possibly inspired by telescopes, they put several lenses in a tube to produce a compound microscope.
Light microscopes have always been limited by the physics of light to 1000× magnification. Far more powerful are electron microscopes, invented in 1931. These microscopes use a beam of high-energy electrons, which have a much shorter wavelength than a beam of light.
The nanoworld was brought into focus by scanning tunnelling (or scanning probe) microscopes, invented in 1981. These work by holding a tip (the probe) about 1 nm from the sample. As the probe moves over the sample, electrons are able to flow, or 'tunnel', between probe and sample, creating tiny electrical currents that can be picked up by sensitive detectors. Moving the probe over the sample picks up the bumps and grooves of the surface, mapping the contours of the nano-landscape.
The atomic force microscope puts the tip on a lever that bends in response to the forces between atoms in the tip and the sample.
These methods cannot only see atoms and molecules, they can also slide them around – as two scientists at IBM did with xenon atoms on a nickel surface to write their company logo.
Optical tweezers can also move particles around. These work in a similar way to Star Trek's tractor beams, using a laser beam to trap particles such as DNA, viruses, bacteria, parts of cells or small metal particles. Strands of DNA can be stretched out to study their elasticity, cells can be moved around, and the force produced by biological motors can be measured.