Viewing a slice of life.

One of the most important advances in optical microscopy was born almost 20 years ago. Since then, however, its development has been stifled by social and political pressures, and only now is it emerging as a powerful tool, capable of providing glimpses into the inner structures of a wide variety of fossil or living matter.

"This machine is particularly desirable," says anatomist David Krause of the State University of New York (SUNY) at Stony Brook, "because we'll be able to look below the surface of fossil teeth without having to damage them physically." Simply focusing the microscope to illumintate a given slice of a translucent specimen has the same effect as grinding away its upper layers. "That will be a major improvement over anything we have been able to do in the past," he says. SUNY expects to get its "tandem scanning reflected-light" microscope next spring.

Making the microscope even more valuable is a new technique for directly recording stereoscopic images at the limit of resolution in optical microscopy. "This approach provides a simple means of photographing translucent specimens to obtain stereoscopic views from which [three-dimensional] aspects of internal structure can be appreciated," says Alan Boyde of University College in London, England. Boyde's report appears in the Dec. 13 SCIENCE.

The idea for the microscope actually goes back almost 20 years. It was invented by Mojmir Petran and Milan Hadravsky of Charles University in Plzen, Czechoslovakia. Petran, who described the design and construction of a prototype instrument in the July 21, 1967 SCIENCE, wanted a reflected-light microscope that would allow him to see processes within the brain cells of living animals.

The scheme involves focusing light into a very thin layer within the object and making sure that only light reflected from that plane reaches the eyepiece. This is the basis for what are now known as confocal microscopes. To get a clear image, a rapidly spinning disk, punctured by thousands of tiny holes arranged in spirals and built into the microscope, generates, a large number of optically sharp spots that the human eye "assembles" into a complete picture.

Few people took this notion seriously at the time, and Petran's career went through a period of serious decline after the Soviet Union's invasion of Czechoslovakia in 1968. Many years later, Alan Boyde visited Czechoslovakia, learned of the microscope and, at the end of 1983, managed to get one for his laboratory in London -- the first microscope of this type outside of Czechoslovakia.

"Were it not for Alan Boyde's interest in it," says Lawrence Martin, "it would never have got into use." Martin, now at Stony Brook, once worked with Boyde.

"With this microscope, we can look at things without destroying them," says Martin. "We can put something the size of an elephant's skull on the microscope and look at its enamel structure." It can even be used to examine the eyes or teeth of a living human being.

"It's the kind of instrument," says Martin, "that almost every biological research laboratory will want to own."