Find out more about the Wellcome Image Awards as well as Wellcome Images, the image library behind the Awards.

Electron microscopy

A beam of electrons is used instead of light to provide information about the structure of the object being viewed. This information is used to create a greyscale image – electrons do not contain information about colour, so any colour in the image is digitally added.

Electron microscopes can achieve magnifications several million times higher than light microscopy, but one major drawback is that living cells and processes cannot be observed. To preserve biological samples for microscopy in their natural condition, they are sometimes rapidly frozen at cryogenic temperatures (lower than −150 °C). This technique is known as cryogenic electron microscopy.

In scanning electron microscopy, electrons are bounced off the surface of the sample to provide details about its composition and topography. For transmission electron microscopy, electrons are passed through an ultra-thin section of the specimen to reveal fine details inside it.

This film features David McCarthy, Manager of the Electron Microscope Unit in the School of Pharmacy at University College London.