The Cryostat, a familiar and vital piece of equipment within histopathology laboratories, is commonly used and operated by thousands of scientists all over the world on a daily basis. Formally known as the Cryo-sectioning system that later evolved in the ’60s, the cryostat is renowned for speeding up the process of examining fresh tissue biopsies directly following surgical operations, making it one of the most pivotal pieces of equipment in histology. But how has this iconic piece of laboratory equipment stood the test of time?


In the 1850s, the methods of tissue examination had changed increasingly following the ‘accidental’ discovery of the first-ever dye, Mauveine. This later led to the development of the ‘Colour Index International’ which standardised staining in 1924. It was the early 20th century when paraffin wax and formalin were first employed to embed and fix tissues. At that time, histopathological diagnoses relied mainly on Haematoxylin and Eosin staining of paraffin sections with the addition of a few standard “special stains” such as the Periodic Acid–Schiff (PAS) reaction for carbohydrates and Perls’ method for iron. This collection of scientific milestones was the conception of the modern histopathology processes that we know today.

For one pioneer, this sparked the need for cutting fresh tissue samples. Professor Dr. A.G. E. Pearse believed there was more than this to the study of cell chemistry. He envisioned a microtome that would be fully integrated into a cold chamber and thus enabling both the cooling or freezing of the fresh tissue sample in conjunction with the cooling of the cutting tool.

With this notion, in 1954 he approached Kenneth Slee the owner of South London Electrical Equipment (SLEE). Together Pearse and Slee developed the first cryostat microtome, in which a Cambridge Rocker microtome was placed inside a refrigerated chamber and all the controls were externalised to help maintain the chamber at a constant temperature of -20 C and to prevent frostbitten fingers. This was a pivotal revolution in medical history; for the first time, it was possible to create high-quality, thin tissue sections from fresh tissue samples. This also meant thin sections of various tissues could be produced extremely quickly, conveniently and precisely. Subsequently improving patient management and speeding up disease diagnosis.

The prototype cryostat, later commercialised as the Pearse–Slee Cryostat and was affectionately known as “Wheezy”. Inevitably, the technology quickly caught on, so as early as 1958, SLEE was the first company in the world to start a series production of cryostat microtomes. Setting the standard in which all cryostats to this day follow.


Cryostats have undoubtedly stood the test of time. Maintaining their traditional functionality whilst evolving to meet the high demand of modern science and advancements in technology.

The founding company and origins of the Cryostat, SLEE medical GmbH, have successfully modified their cryostat over the years to meet the needs of scientists and uphold their well-earnt status. Their MEV Semi-Automatic and MNT Fully Automatic Cryostats are ergonomically built to ensure they are suitable for all size users whilst keeping their original floor standing position.

On a day-to-day basis, surgeons and scientists are up against the pressures of time. They are always scouting for the best equipment and tools that will enable them to speed up processes and improve the quality of results.

SLEE prioritises the original objectives when it comes to any modifications to the Cryostat; ensuring their sole purpose is to cut fast biopsies for the investigation of any abnormal growths or tumours discovered. The microtome inside is capsulated in stainless steel to avoid any interruptions caused by the pollution of condensation or moisture and prevent downtime from any damage to the machine.

Scientists have also embraced automation to process a larger number of samples with greater speed and precision. The MNT and MEV Cryostat have adapted their functionality to provide either semi-automatic or fully automatic as an alternative to the traditional manual hand course wheel, which still remains. The high-precision rotary microtome is motorised with up to 750μm advance/return, offering the largest μm capacity on the market, to accommodate both medical and industrial applications. The motorised sectioning contributes to the increased speed of output, enabling reports from fresh tissue samples to return as quick as 25-30 minutes.

The low freezing capacity of -35°C, means the SLEE Cryostats can process a sample by freezing, cutting and sectioning a specimen all within 5 minutes, minus any staining. With no exception to the type of specimen being processed, an additional accessory provides freezing temperatures of -55°C enabling fast freezing of fattier samples such as; breast tissue, kidney or liver samples. Faster freezing without nitrogen also reduces the risk of ice crystals forming and prevents scratching and loss of samples.


Over time, Cyrostat’s have enabled histopathologists to study the margins of cancer, provide a quick diagnosis of the condition of tissue sections, examine enzyme histochemistry to diagnose and treat neuromuscular diseases and immunohistology. The Cryostat has remained a timeless piece of equipment in laboratories, that has successfully met the needs of scientists and will remain so throughout time. But why is this? This is because, collectively, cryostats have delivered results, efficiently and environmental from the offset. The freezing shelf within the cryostat offers 24 positions for specimens, enabling multiple specimens to be processed from different operations at the same time. This means processes are more time-efficient and scientists or surgeons are able to act fast according to results and deliver the best care to their patients.

Not only do laboratories have the responsibility to patients, but as standards change and evolve, they also have the responsibility to ensure that their laboratory and equipment meet requirements. This can play a huge part in the lifespan of equipment within a lab. An advantage to the SLEE Cryostat is that they do not require paraffin in order to hold and section a sample, making use of more environmentally friendly products to operate.

The world and surrounding environment is continuously changing and evolving. And it would seem that it is happening faster than ever, that it is now a matter of keeping up. With more enhanced technology and automation it is important that equipment does not fall out of date. For any machine or equipment to maintain its position, manufacturers need to ensure that they are adapting and modifying with the movements. In doing this successfully, without jeopardising the objectives of its basic function, there is no doubt that any machine, like the Cryostat, can stand the test of time. This is proven by SLEE, who have continued to evolve and improve the Cryostat from its first commercial version in 1954 to the present day.