Research at The Natural History Museum often involves the study of microscopic features of plants, animals and minerals. Electron microscopes are capable of imaging specimens at very high magnifications.
Scanning electron microscope
The scanning electron microscope uses a focused beam of electrons, in a vacuum, to scan across the surface of specimens. This generates a signal which is displayed as an image on a monitor which can then be photographed or recorded electronically. Lenses made from electro-magnets are used to focus and change magnification.
The specimens are normally coated with a metal, such as gold or
platinum, before they are placed in the microscope. This helps to
provide a high quality image which is needed for the very high
magnifications Museum scientists use for their research.
The scanning electron microscope pictured to the right is made by Hitachi and can magnify from 20 to 300,000 times. The Museum has three other scanning electron microscopes, a transmission electron microscope and an electron microprobe analyser.
Examples of some of the images taken in the electron microscopy
unit can be seen below:
Pollen grains
These horse chestnut pollen grains were frozen before they were
examined in the electron microscope. This allowed them to be
studied in their natural state of hydration.
Chloroplast
Chloroplasts are found in the leaves and green stems of plants.
They are the site of photosynthesis. In the electron microscope
their complex structures can be examined.
