PEERING INThe new light microscope could clearly see the mitochondria. Using fluorescent orange dyes the microscope revealed that a particular protein was clustered around the outer surfaces of the mitochondria.S. Hell, Nature Methods

Scientists have made a powerful version of the light microscope that can peer into a living cell.

Until now, the ordinary light microscope couldn’t clearly see objects smaller than about 200 nanometers by 600 nanometers – about one-tenth of the size of the average bacterium. While that seems tiny, it’s bigger than many of the parts inside a cell. In contrast, the new microscope can image objects that are as small as 40 nanometers across, says Stefan Hell, a physicist at the Max Planck Institute for Biophysical Chemistry.

“If we could see objects that were as big as a football before, now we can see objects the size of a tennis ball,” Hell says.

This microscope may allow researchers to watch proteins assemble inside cells, says Peter So, a biological engineer at MIT who was not involved in the study. “This will allow us to look at the dynamics inside cells with three-dimensional resolution,” So says.

Before now, the only way to see the three-dimensional interior of a cell was to use an electron microscope. Scientists had to work with long-dead cells, slicing the cells and then painstakingly coating each slice with metal to view them with the electron microscope, says Hell. To get a picture of the 3-D underlying structure, each slice image had to be re-assembled into a single image by computers.

Using the new microscope, however, Hell and his colleagues were able to view the mitochondria, the energy power house of the cell, the team reports in the May 18 Nature Methods. The images showed the mitochondria in greater detail than older light microscopes could, while preserving the cell’s 3-D structure.

The microscope takes advantage of a fluorescent dye, which researchers injected into the cell to visualize the location of a particular protein inside the mitochondria.

The next step, Hall says, is to apply the technology to live-cell imaging and to make a more detailed map of the cell.

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