A team from Vanderbilt University in the US have machined silicon to make what is claimed to be the world's smallest version of the periscope.
"With an off-the-shelf laboratory microscope you only see cells from one side, the top," said biologist Chris Janetopoulos. "Not only can we see the tops of cells, we can view their sides as well - something biologists almost never see."
The trick has been making pyramidal-shaped cavities in silicon whose interior surfaces are coated with a reflective layer of gold or platinum.
"This technology is exciting because these mirrored wells can be made at very low cost, unlike other more complex methods for 3D microscopy," said biomedical engineering Kevin Seale.
The Vanderbilt group is not the first to make microscopic pyramidal wells, but it is the first to apply them to make 3D images of microorganisms.
In 2006, a group of UK scientists created pyramidal micromirrors and applied them to trapping atoms, said Vanderbilt, and last spring researchers at the US National Institute of Standards and Technology used similar structures to track nanoparticles.
So far, the researchers have used the mirrored wells to examine how protozoa swim and cells divide. "The method is particularly well suited for studying dynamic processes within cells because it can follow them in three dimensions," said Janetopoulos.
Now there are plans to create mirrored microchannels to measure how fluid flow affects cell behaviour and attachment.
According to Janetopoulos, the micro-pyramids also have a major advantage for single molecule studies. Optical noise is a constant problem when working at the low light levels involved. Being able to pinpoint actual light sources in two or three dimensions allows the researchers to reject spurious signals.
