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Découvrir les sciences de la vie

  • Off the Bench
  • Inspirer la science
  • Témoignages

With his microscope, biologist Gary Greenberg discovers the world a new each day. His favorite object: sand.

Gary Greenberg was cleaning out his office when he came across a film cannister full of sand. His brother David had sent it to him from Maui to freezing Philadelphia. This was where Gary was busy making accessory devices that converted 2D microscopes into 3D microscopes. On the brink of tossing out the can, he suddenly thought, „I wonder what this looks like in the microscope?“

What he beheld through the eyepiece amazed him. How could each individual grain be so unique, so colorful, so beautiful – and so different from what we, at first glance, perceive to be mere sand? As a scientist, he was not satisfied with a single “sample”, and he asked a friend to send him sand from the Virgin Islands. It turned out to be astonishingly different. Each grain brought Greenberg closer to the realization that even seemingly banal items may harbor exceptional secrets – secrets that are hidden from view. “I was hooked”, recounts Greenberg. “I asked all my friends to send me sand and started photographing these little jewels.“

Sand from the Moon

For Greenberg, the physically loose sediments with a grain size of between 0.063 and 2 millimetres are unique gems. They are formed when rocks weather physically or chemically and occur to varying degrees on the entire earth's surface. At Greenberg, for example, sand from Japan to Belgium was now also on the microscope slide.

What fascinates the scientist most, however, is a specimen from even further away: moon sand, collected by NASA® during its "Apollo" missions. Greenberg’s book on sand had come to the attention of the Space Agency, which first provided him with samples and later with a grant to photograph the lunar sand. While the latter consists of the same minerals as those found in the Earth’s crust, its appearance is vastly different: it is darker and is reminiscent of shimmering metal, instead of appearing glossy and resembling precious stones, like most terrestrial sand. This difference is rooted in their creation: “The lunar surface is continually bombarded by meteors and micrometeorites“, explains Greenberg. “so there are darker glassy mineral sand grains produced by the heat and pressure of these collisions.“

Microscopic improvements

Earth itself still holds plenty of secrets, and more laws of nature are waiting to be discovered. Long before sand, Greenberg had been searching for the precise way to visualize things. In the eighties, during his time as assistant professor at the University of Southern California®, he researched the formation of birth defects by studying tissue. He regretted the lack of depth of the two-dimensional images that were generated by the microscopes available to him. He began experimenting with their illumination system by changing the angle at which the light hit the sample. Depth of field improved dramatically. With this discovery, Greenberg initiated the development of his own 3D microscopy, for which he holds 20 US-patents today. His company, Edge-3D, equips industry and research with instruments that are used in such diverse areas as neuroscience, geology and pathology. They continue to uncover secrets that are right under your nose. All you have to do is look closely.


Dr. Greenberg, why is it worth looking at sand through one of your 3D microscopes?

Gary Greenberg:
Conventional microscopes can only provide 2D images with extremely limited depth of focus. Only a very thin slice of the specimen can be seen in focus at one time. 3D microscopes automatically take a sequential series of photographs of the specimen at different focus levels. A software then combines the individual photographs to generate an image that is entirely in focus and that can be viewed in 3D on the screen.
Are there advantages to other areas?

Yes, for investigations of objects that are naturally thick and complex. They are particularly useful in areas such as neurobiology, developmental biology, cancer biopsies, plant biology, geology and live-cell tissue culture.


Because of the shallow depth of focus of 2D microscopes, microscopists usually prepare 5-micron sections of their samples to eliminate the problem of out-of-focus blur. This is problematic because the average cell is between 10 and 30 microns. Examining 5-micron sections leads to under-sampling errors, resulting in misinterpretation of the data.

Book suggestion

The Secrets of Sand“A new face of the world is presented in the book by Gary Greenberg, Carol Kiely and Kate Clover. The microscopic images of sand from the Earth to the Moon convey not only undiscovered beauty, but they also reveal new fascinating facts about our planet.

The Secrets of Sand, 128 pages, Publisher:

Voyager Press, aprox. 18,99 Euros,

ISBN-13: 978-0760349441