Core Facility Electron Microscopy of Charité Berlin
The Charité Core Facility for Electron Microscopy (CFEM) in Berlin is your contact for professional advice and the use of infrastructure for conducting electron microscopy projects. We offer a wide range of electron microscopy techniques for scientific projects.
Our facility provides assistance to users in project planning and implementation (sample fixation and preparation) as well as data analysis. Our services include individual user training and the execution of projects as full-service offerings. This means that all necessary tasks (sample fixation, preparation, and image documentation on electron microscopes) are performed by CFEM staff.
Our portfolio includes classical transmission electron microscopy (TEM), scanning electron microscopy (REM), cryopreparation techniques (cryosubstitution, cryo-ultramicrotomy), immune-electron microscopy (Immune-EM), cryo-electron microscopy (cryo-EM), and electron tomography.
For more information, including user regulations and scheduling fees, please visit our homepage. If you have any further questions, we are happy to assist you. Please contact us at cfem(at)charite.de.
What is an electron microscope?
An electron microscope enables the direct imaging of objects with very high resolution.
The resolution of light microscopy is constrained by the wavelength utilized; electron microscopy overcomes this limitation by employing electrons instead of visible light, thereby achieving a remarkable resolution limit of ≤ 0.1 nm. This limit is solely dependent upon the biological characteristics of the specimen under examination.
What types of electron microscopes exist?
Since the invention of the first electron microscope by Ernst Ruska in Berlin in 1932 at the Technical University of Berlin, electron microscopy has steadily evolved. Essentially, two principles can be distinguished, which are also known from light microscopy: transmitted light microscopy and reflected light microscopy.
In transmission electron microscopy (TEM), an electron beam emitted from an electron source passes through the sample. By using electromagnets in series, an enlarged image of the object is achieved. This image is formed when the electrons passing through the sample are absorbed and scattered to different degrees depending on their properties and density. Therefore, it is important that the sample is transparent to the electron beam, so the sample thickness does not exceed a certain value. Larger or thicker objects are embedded in a time-consuming process (dehydration, infiltration with liquid plastic). Ultra-thin sections (<100 nm) are then made from the hardened sample using an ultramicrotome, which can then be examined by the TEM. A high vacuum is used In the electron microscope, since the presence of atmospheric oxygen can lead to interactions with the heated electron emitter during imaging.
Electron microscopes that can display the surface of objects are called scanning electron microscopes (REM). In this case, a focused electron beam scans the sample in a uniform pattern and produces secondary electrons (SE) as well as backscattered electrons (BSE). Special detectors detect the emitted electrons and create an image of the object line by line. As with TEM, high vacuum is also used in REM.