High pressure freezing is a sophisticated method to fixate biological material like tissue and cells. With the HPF the specimen is rapidly frozen by simultaneously applying a high pressure. The cooling rates achieved are in the order of 10000 K/sec. The operating pressure during the cooling process is increased to 3000 bar. Under these extreme conditions the aqueous phase in the specimen can´t crystallize but is vitrified instead. With this method samples up to 200 µm thickness can be prepared without any prefixation or additional cryo-protectants.