Watch Video of a Developing Embryo

For the first time, it is possible to actually watch the initial 24 hours of the life of an embryo at the cellular level.

With a newly developed microscope that uses a sheet of light to scan a living organism from many different dimensions, scientists were able to track the complex cellular organization of a zebrafish embryo as it grows from a single cell to 20,000 cells.

"Imagine following all inhabitants of a town over the course of one day using a telescope in space," Philipp Keller of the European Molecular Biology Laboratory in Heidelberg, Germany, said in a press release.

"This comes close to tracking the 10 thousands of cells that make up a vertebrate embryo."

Previously, scientists had only been able to piece together the first hours of a couple invertebrate organisms with only a few hundred cells such as a nematode worm -- work that resulted in a Nobel Prize. But doing the same for a vertebrate animal was essentially impossible.

The montage (above) of three-dimensional images taken at 10-minute intervals shows cells dividing and moving around the embryo to form specialized tissues from two different angles. The new research was published today in Science.

"The digital embryo is like Google Earth for embryonic development," Jochen Wittbrodt of the University of Heidelberg said in a release. "It gives an overview of everything that happens in the first 24 hours and allows you to zoom in on all cellular and even subcellular details."

The new technique, called Digital Scanned Laser Light-Sheet Fluorescence Microscopy, could be used on other animals such as mice, chicken and frogs, which would could help researchers better understand evolution at the cellular scale.

Already, the research has shown that the initial stages of heart development do not happen as scientists thought.

Video: European Molecular Biology Laboratory