What Is a Cryostat?

A cryostat — more precisely a cryostat microtome — is a refrigerated instrument that cuts extremely thin sections of frozen, unfixed tissue for microscopic examination. It exists to solve a timing problem that standard histology cannot: routine tissue processing (chemical fixation, paraffin embedding, then sectioning) takes many hours to a full day, but a surgeon waiting on a margin result mid-operation, or a researcher who needs tissue morphology preserved without fixative, cannot wait that long. A cryostat freezes a small tissue sample solid in seconds to minutes and sections it inside a refrigerated chamber, producing a slide a pathologist can read in roughly 10–20 minutes from the moment tissue arrives in the lab.

What a Cryostat Actually Does

Structurally, a cryostat is a microtome (a precision instrument that advances tissue past a blade in controlled, extremely thin increments) enclosed inside an insulated, mechanically refrigerated cabinet. A small piece of tissue is mounted on a metal chuck, typically embedded in OCT (optimal cutting temperature) compound — a water-soluble gel that solidifies at low temperature and holds the tissue in a cuttable orientation without the chemical fixation or dehydration that paraffin processing requires. The chuck is rapidly frozen, then advanced past the internal blade in micron-scale increments, exactly as a standard microtome would, except the entire cutting mechanism sits inside a chamber held well below freezing so both the tissue and the blade stay cold and cuttable throughout. The resulting sections are lifted onto a glass slide, briefly fixed and stained — usually with a rapid H&E (hematoxylin and eosin) protocol — and read under a microscope, all within the same short window.

Who Uses One, and Why

The dominant clinical use is intraoperative frozen section consultation: while a patient is still on the operating table, a pathologist uses cryostat-cut sections to tell the surgical team whether excised tissue margins are clear of tumor, to identify unexpected tissue, or to confirm a lesion before the surgeon decides how much more tissue to remove. That single use case is why cryostats sit in or near surgical pathology suites in essentially every hospital that performs oncologic surgery. Outside the OR, cryostats are standard equipment in research histology, because several techniques — immunofluorescence, many antibody-based immunohistochemistry protocols, in situ hybridization, and work with lipid-rich or enzyme-sensitive tissue — depend on antigens or structures that chemical fixation and paraffin heat can degrade or mask. Freezing preserves them instead. Veterinary diagnostic labs and forensic pathology use cryostats for the same reasons: speed, and preservation of fixation-sensitive detail.

Cryostat vs. Microtome: What’s the Actual Difference

This is the single most common point of confusion, and the short answer is that a cryostat is a microtome — a specialized, refrigerated one built for one job. A standard (rotary) microtome, covered in depth in our companion guide on what a microtome is, cuts tissue that has already been chemically fixed and embedded in paraffin wax, at room temperature, and is the workhorse of routine, non-urgent histology — the slower, more involved process that produces the higher-detail, longer-lasting archival slides used for most diagnostic and research work. A cryostat trades some of that section quality and long-term archival stability for speed: frozen sections are read within minutes rather than the next day, at the cost of somewhat coarser morphology and sections that don’t keep well long-term. In practice, most pathology labs run both: a cryostat for anything that needs a same-encounter answer or unfixed tissue, and a standard microtome for the routine paraffin workflow that follows.

Cryostat vs. Ultra-Low-Temperature (ULT) Freezer: A Different Kind of Confusion

Because both sit in the general category of “cold lab equipment,” a cryostat is easy to mix up with an ultra-low-temperature freezer — but the two share almost nothing functionally. A ULT freezer, typically running around -80°C, is a passive storage appliance: it holds samples — DNA, cell lines, reagents, biobank specimens — for months or years and has no cutting mechanism, no microtome, and no role in producing a slide. A cryostat is an active sectioning instrument: its refrigeration exists only to keep tissue and blade cold enough to cut cleanly, not to store anything long-term, and tissue typically stays in it for minutes, not months. If your lab is choosing between the two, the question that actually matters is whether you need to store something cold or cut something frozen — they are not substitutes for each other. (Liquid-nitrogen-based cryogenic storage, covered in our cryogenic storage and dewar safety guide, is a third, related-but-distinct category again, used for sample types that even a -80°C freezer can’t adequately preserve.) It’s also worth noting that “cryostat” is a term borrowed from physics and engineering more broadly, where it refers to any device that maintains a cryogenic temperature — the cooling system around an MRI machine’s superconducting magnet is also called a cryostat. That usage is unrelated to the histology instrument this guide covers, but it’s a common source of search confusion worth naming.

Practical Relevance for Lab Management and Procurement

For a research-administration or lab-management audience, a few considerations distinguish cryostat planning from ordinary equipment purchases. Because cryostats section unfixed, potentially infectious tissue, biosafety matters more here than for most bench instruments: look for a built-in UV decontamination cycle, an antistatic chamber, and a documented cleaning/defrost protocol, particularly if the lab works with known-infectious or high-risk specimens. Placement matters too — a cryostat used for intraoperative consultation needs to sit close enough to the operating suite that turnaround time stays under the clinical target, which is as much a facilities-planning question as an equipment one. In a regulated clinical lab, bringing a new cryostat into service typically goes through the same installation/operational/performance qualification (IQ/OQ/PQ) process used for other diagnostic instruments; see our broader guide on lab equipment planning and qualification for how that process generally works. Staffing is a real factor as well: frozen sectioning is a distinct technical skill from paraffin histotechnology, and turnaround-time targets for intraoperative consultation depend on having a technologist specifically trained on the instrument, not just general histology experience.

Related Lab Equipment

A cryostat is one piece of a larger tissue-processing and imaging workflow. For bulk tissue disruption ahead of molecular extraction (protein, RNA, or DNA) rather than thin-section imaging, labs typically reach for a homogenizer instead — the two solve different problems even though both process tissue samples. Downstream, sections cut on a cryostat are sometimes digitized for telepathology or AI-assisted review; see our guide on digital pathology scanners for that step. And for the routine, non-urgent side of histology that a cryostat complements rather than replaces, see the companion guide on what a microtome is linked above.

Frequently Asked Questions

What is a cryostat used for?

Primarily for intraoperative frozen section diagnosis in surgical pathology — giving a surgical team a rapid read on tissue margins or tissue identity while a patient is still in the operating room — and for research histology techniques (immunofluorescence, in situ hybridization, and other fixation-sensitive protocols) that require unfixed, frozen tissue rather than paraffin-embedded tissue.

What is the difference between a cryostat and a microtome?

A cryostat is a specialized, refrigerated microtome. A standard microtome cuts chemically fixed, paraffin-embedded tissue at room temperature for routine histology; a cryostat cuts unfixed, frozen tissue inside a cold chamber, trading some section quality for a turnaround measured in minutes instead of a day.

Is a cryostat the same as a freezer?

No. A cryostat is an active cutting instrument used to section frozen tissue; an ultra-low-temperature freezer is a passive storage appliance with no sectioning function, used to hold samples for months or years rather than minutes.

What temperature does a cryostat run at?

Cryostat chambers run well below freezing, with the exact setpoint adjusted for the specific tissue type being cut — fatty or soft tissue generally needs a colder setting than dense tissue to section cleanly. The precise range varies by manufacturer and protocol, which is why frozen-section technologists typically work from a tissue-specific temperature reference rather than a single fixed number.