What is histology in the laboratory?

2026-07-30 — Equipo JP Selecta

In the field of health sciences and biotechnology, understanding what histology is proves essential in order to analyse how biological structures are organised at microscopic level. Far from being merely a theoretical discipline, the preparation and analysis of tissues in the clinical and industrial environment directly condition medical and research decision-making.

Carrying out a rigorous histological study makes it possible to do everything from diagnosing complex pathologies such as tumours to driving biomedical research and certifying quality control in the agri-food and pharmaceutical industries. In this article we will review its fundamentals, the step-by-step process for processing a sample and the technical equipment needed to carry it out.

What is histology?

To arrive at a precise definition of histology, we can describe it as the branch of biology and medicine devoted to microscopic anatomy, that is, to the study of the structure, composition and function of organic tissues.

In everyday laboratory practice, confusion often arises between three concepts that should be clearly delimited:

• Macroscopic anatomy: studies organs, apparatus and systems with the naked eye, analysing their shape, size and location in the body.
• Histology: analyses the three-dimensional architecture of cells when they group together and interact to form organised tissues.
• Cytology: focuses exclusively on the morphology and alterations of isolated or shed cells (as in a cervical smear), without assessing the overall tissue structure.

Therefore, the key to histological analysis lies in keeping the tissue architecture intact in order to understand how cells behave within their original matrix.

What does histology study?

The central object of study of this discipline covers the characterisation of the four fundamental types of tissue that make up the animal and human organism:

• Epithelial tissue: lines body surfaces and internal cavities and forms the glands.
• Connective tissue: provides structural support, joins, protects and nourishes the other tissues (including bone, cartilage, blood and adipose tissue).
• Muscle tissue: specialised in contraction and force generation (skeletal, cardiac and smooth).
• Nervous tissue: formed by neurons and glial cells, devoted to the transmission of electrochemical impulses.

Histology examines the direct relationship between the geometry of these microscopic structures and the physiological function they perform in the healthy or diseased body.

Bear in mind: the difference between normal histology and histopathology

Within sample analysis it is essential to distinguish the biological state of the tissue examined:

• Normal histology: describes the morphology, arrangement and cellular patterns characteristic of a completely healthy tissue.
• Histopathology: is the applied branch of pathological anatomy that studies altered or diseased tissues. Its analysis makes it possible to identify inflammation, necrosis, degenerative processes, infections or benign and malignant tumour lesions.

What does a histological study involve?

Processing a biological sample so that it can be observed under an optical microscope requires transforming a soft, unstable piece into a transparent, rigid and stained section just a few microns thick.

The standard workflow in the laboratory consists of five sequential stages:

• Sample collection and fixation: after the biopsy or surgical specimen has been taken, the sample is immediately immersed in a chemical fixative (usually 10% buffered formaldehyde) to halt cellular autolysis and preserve the tissue structure.
• Dehydration and paraffin embedding: the fixed sample is passed through increasing grades of alcohol to remove water and is then cleared with an intermediate agent (such as xylene). Next, it is impregnated and embedded in hot liquid paraffin inside a mould, and the mixture is left to cool to obtain a solid, manageable block.
• Sectioning with a microtome: the frozen or hardened paraffin block is placed in a microtome, a precision instrument fitted with a sharp blade that produces ultra-thin sections between 3 and 5 microns thick.
• Staining: as tissues are transparent, the sections obtained are mounted on glass slides and subjected to biological dyes to contrast the nuclei, the cytoplasm and the extracellular matrix.
• Mounting and observation: the stained sample is covered with a coverslip using a synthetic mounting resin and analysed under the optical microscope or digital scanner.

Most common staining techniques

Applications of histology

The usefulness of the microscopic analysis of tissues spans multiple fields of science and industry:

• Anatomopathological diagnosis: it is the standard for confirming or ruling out malignancy in tumour biopsies, staging chronic pathologies and guiding oncological treatments.
• Biomedical research: it makes it possible to understand the mechanisms of action of new drugs, analyse animal models of disease and develop tissue engineering.
• University teaching: essential in the training of medical, veterinary, biology and nursing students.
• Quality control and the food industry: used to detect fraud or unauthorised additions in meat derivatives (such as the undeclared presence of offal, meals or cartilage).
• Veterinary medicine: Applied to pathological diagnosis and epidemiological control in production and companion animals.

Equipment needed for a histology laboratory

To complete this workflow while guaranteeing maximum repeatability and preservation of the samples, a specific instrumental chain is required to maintain efficiency of work in the laboratory:

• Paraffin dispensers and embedding baths: They keep the paraffin at a constant temperature of between 50 °C and 100 °C to melt the polymer without degrading it, making it easier to fill cassettes and moulds quickly.
• Block cooling plates: Cold surfaces (capable of reaching sub-zero temperatures) that speed up the solidification of the paraffin to firm up the block before sectioning.
• Microtomes: Mechanical or automatic equipment with micrometric advance to obtain homogeneous, continuous tissue sections.
• Flotation baths: Dark-surfaced water baths that allow paraffin ribbons to be spread over hot water (at around 40-45 °C) to remove wrinkles before picking up the section on the glass slide.
• Hot plates for drying slides: Flat-surfaced thermal plates that make it possible to fix the sample to the glass and evaporate excess water before starting the staining baths.
• Staining dishes, baskets and racks: Vessels made of glass or inert plastic materials designed to immerse series of slides in dewaxing reagents, alcohols and dyes.

Pathological anatomy and histology laboratories usually rely on specific histology equipment for each phase of the process, such as that manufactured by J.P. Selecta, with compatible accessories and consumables to complete the workflow safely and efficiently.

Frequently asked questions

• What is the difference between histology and pathology?

Histology studies the microscopic structure and composition of healthy tissues. Pathology (or pathological anatomy) is the medical speciality that studies diseases and their manifestations; when pathology analyses tissues microscopically in order to diagnose, it uses histopathology as its analytical technique.

• How long does a histological study take?

A routine study by paraffin embedding usually takes between 24 and 48 hours because of the time needed for fixation, dehydration and impregnation of the tissue. In cases of extreme intraoperative urgency, a frozen section (intraoperative biopsy) is performed, which makes it possible to obtain an indicative diagnosis in 15 to 20 minutes.

• What is a histological biopsy?

It is the removal of a small sample of living tissue from a patient (by puncture, aspiration, endoscopy or surgery) in order to subject it to full histological processing and determine the nature of a lesion.

• What role does histology play in the food industry?

It makes it possible to authenticate raw materials by checking for the presence of tissues belonging to the declared species and detecting the fraudulent inclusion of unauthorised meat by-products, vegetable filler fibres or thermal alterations not permitted in the processing chain.