What Is a Microtome?

A microtome is a laboratory instrument built to cut extremely thin, uniform slices of tissue or other material — typically a few micrometers thick — so the slice is thin enough for light to pass through it under a microscope. Tissue is opaque and structurally messy in bulk; a microtome turns a block of it into a section thin enough to mount on a glass slide, stain, and examine cell-by-cell. It’s the instrument that sits between “we have a tissue sample” and “we can actually look at its cellular structure,” which is why it’s foundational to histology and diagnostic pathology rather than a niche accessory.

What a microtome does and why it exists

Before a tissue sample can be examined under a standard light microscope, it has to be thin enough for light to pass through — a whole biopsy or organ slice is far too thick and opaque. A microtome solves that by holding a prepared tissue block steady against a very sharp blade and advancing it in tiny, precise increments (commonly in the single-digit-micrometer range for routine histology, adjustable on the instrument), shaving off one uniform ribbon-like section at a time. Each section is then floated onto a water bath, mounted on a glass slide, stained, and read under a microscope. Without that step, the rest of histology — H&E staining, immunohistochemistry, cancer margin assessment, basic tissue research — has nothing to work with.

Main types of microtome

The right type depends on how the tissue was prepared and how fast a result is needed:

• Rotary microtome — the standard workhorse of a histology lab. The tissue block (usually embedded in paraffin wax for support) is mounted on a wheel that the operator turns; each full rotation advances the block past a fixed blade and produces one section. This is what most people picture when they hear “microtome,” and it’s the instrument behind routine diagnostic pathology and most fixed-tissue research sectioning.
• Cryostat (frozen-section microtome) — a microtome mounted inside a refrigerated cabinet, used to section fresh, unfixed tissue that’s been rapidly frozen instead of paraffin-embedded. Because freezing is much faster than paraffin processing, a cryostat can turn a tissue sample into a readable slide in minutes rather than the better part of a day — the reason it’s the instrument used for intraoperative “frozen section” diagnosis while a patient is still on the operating table. See the dedicated What Is a Cryostat? guide for how the refrigerated cabinet, cutting mechanics, and frozen-section workflow specifically work.
• Sliding or sledge microtome — the blade (or the block) travels along a horizontal track rather than a rotating wheel. Often used for larger or harder specimens, including some non-paraffin-embedded and whole-mount work.
• Vibrating microtome (vibratome) — uses a rapidly oscillating blade to section fresh or lightly fixed tissue that hasn’t been embedded at all, common where embedding chemicals would interfere with the downstream assay (some live-tissue and electrophysiology work, for example).
• Ultramicrotome — a specialized instrument for the much thinner (nanometer-scale) sections electron microscopy requires, using glass or diamond knives instead of a standard steel blade. It solves a related but distinct problem from a standard microtome and is usually treated as its own equipment category.

For most research-administration and lab-management purposes, “microtome” without qualification means the rotary microtome, and the meaningful disambiguation a searcher usually needs is the one below.

Microtome vs. cryostat: what’s actually different

This is the single most useful clarification on this topic, because the terms get used almost interchangeably in casual conversation despite naming two different things. A cryostat is not a separate category of instrument from a microtome — it is a microtome, housed inside a refrigerated cabinet so it can cut frozen tissue instead of paraffin-embedded tissue. The cutting mechanism is fundamentally the same rotary-advance-and-blade action; what changes is the environment around it and the tissue-preparation method it’s built to pair with:

• A standard rotary microtome sections paraffin-embedded tissue at room temperature. Preparation (fixation, processing, wax embedding) typically takes many hours to over a day, but the resulting sections are well-preserved and hold up well for archival and detailed diagnostic work.
• A cryostat sections frozen tissue inside a chilled cabinet, in minutes. It trades some morphological detail and tissue preservation quality for speed — the right tradeoff when a surgeon is waiting on a diagnosis, or when a research protocol needs the tissue’s antigens or nucleic acids intact and unaltered by the heat and solvents paraffin processing involves.

If a page, protocol, or purchase order says “cryostat,” it’s describing a specific, refrigerated variant of a microtome built for frozen sections — not a different category of lab equipment.

Common uses in histology and pathology

Microtome sectioning underlies most tissue-based diagnostic and research work:

• Surgical and diagnostic pathology — routine biopsy processing, cancer diagnosis and margin assessment, and rapid intraoperative frozen-section consultation (via cryostat) that informs a surgeon’s decisions in real time.
• Biomedical and preclinical research — histology is a standard readout in animal studies, drug-toxicity assessment, and basic biology, wherever a researcher needs to see tissue architecture, cell counts, or the localization of a stain or antibody signal rather than just a bulk measurement.
• Immunohistochemistry (IHC) and in situ work — these techniques are read on sectioned tissue, so section quality and thickness consistency from the microtome step directly affect how interpretable the final stained slide is. (See the site’s IHC protocol and troubleshooting guide for how downstream staining depends on getting this step right.)
• Veterinary and agricultural diagnostics — the same sectioning workflow supports animal-tissue diagnosis and research outside human medicine.

Who uses a microtome

In a clinical setting, histotechnologists and pathology-lab staff run the sectioning as a routine, high-volume production step, with pathologists reading the resulting slides. In a research setting, the operator is more often a lab technician, graduate student, or dedicated histology-core staff member, since consistent, artifact-free sectioning takes real hands-on skill to learn — thin, uneven, or torn sections are a common source of unusable slides for a new operator.

Practical relevance for research administration and lab management

A microtome (and especially a cryostat) is a capital purchase and an ongoing maintenance line, not a one-time cost: blades need regular replacement or resharpening, cryostats need periodic defrosting and temperature-calibration checks, and both need documented cleaning between specimens to avoid cross-contamination between samples — a real concern in any shared-use core facility processing tissue from multiple studies or patients. For a lab manager or research-administration reader, that means budgeting for consumables (blades, embedding media, slides) alongside the instrument itself, and treating a shared microtome or cryostat the same way as any other shared instrument with a documented maintenance and usage log: a section that’s inconsistently thick or torn doesn’t fail loudly, it just produces a slide that reads poorly or a stain that looks artifactually wrong, which can be hard to distinguish from a real biological finding if nobody is tracking the instrument’s own maintenance history.

Related equipment

A microtome is one step in a broader tissue-handling workflow, and it’s often confused with or paired against equipment that does a genuinely different job:

• Cryostat — as covered above, a refrigerated microtome for frozen sections rather than a separate instrument category. See What Is a Cryostat? for the dedicated deep-dive.
• Homogenizer — does essentially the opposite job. Where a microtome preserves tissue architecture by cutting it into thin, intact sections for imaging, a homogenizer physically disrupts tissue into a uniform slurry or lysate, destroying the structure on purpose so the sample can be used for extraction-based assays (protein, RNA, DNA) instead of microscopy. See What Is a Homogenizer? for that side of tissue processing.
• Microscope — the instrument the microtome’s output is made for. A section is only useful once it’s mounted, stained, and examined; see What Is a Microscope in a Research Lab? for the instrument on the other end of this workflow.

Frequently asked questions

What is a microtome used for?

Cutting tissue or other material into extremely thin, uniform sections thin enough to examine under a microscope — the essential preparation step behind histology, surgical pathology diagnosis, and most tissue-based biomedical research.

Is a cryostat the same as a microtome?

A cryostat is a specific type of microtome — one built inside a refrigerated cabinet to section frozen, unfixed tissue rather than paraffin-embedded tissue, trading some tissue preservation for a much faster turnaround. See What Is a Cryostat? for the full comparison.

What’s the difference between a rotary microtome and a cryostat?

A rotary microtome sections paraffin-embedded tissue at room temperature, a process that takes many hours of preparation but preserves tissue detail well. A cryostat sections frozen tissue inside a chilled cabinet in minutes, which is why it’s used for rapid intraoperative diagnosis, at some cost to morphological detail.

How thin does a microtome cut?

Routine histology sections are typically in the single-digit-micrometer range, thin enough to mount on a slide and pass light through under a microscope; the exact setting depends on the tissue, the embedding method, and what the downstream stain or assay requires. An ultramicrotome, used for electron microscopy rather than light microscopy, cuts far thinner, nanometer-scale sections and is treated as a distinct instrument category.

Who typically operates a microtome?

In clinical pathology labs, histotechnologists run sectioning as routine, high-volume work; in research settings, it’s more often a trained lab technician, graduate student, or histology-core staff member, since consistent sectioning takes real hands-on skill to learn.