What is Histology?

Every plant and animal life form is composed of tissues, and the study of these tissues is referred to as histological study. A histologist specializes in examining all different configurations of these biological tissues at every layer of the organism, both in terms of complete vital organs and the base molecules themselves.

Different Categorizations

Depending on the particular nature of the life form in question, a histologist will observe the tissues composing it under the lens of a certain distinguishing categorization. Collenchyma, sclerenchyma, support tissue, photosynthetic tissue, vascular tissue, and other undifferentiated variations make up the categories of plant tissues. The cell tissue categories of animals include (but are not limited to) epithelial tissue, connective tissue, blood cells, nervous tissue and muscle tissue.


The roots of the practice can be traced back to the studies of Italian inventor Marcello Malpighi, credited for being behind the creation of one of the very first microscopes in the 17th century. With his microscope, Malpighi was able to conduct observations of the deep microscopic structures composing small animals such as frogs. Upon Malpighi’s observation of connective bridges between arteries and veins in the lungs, he deemed them capillaries. Malpighi’s discovery laid the foundation for modern science’s understanding of the oxygen absorption qualities of the blood.

Divisions in the Field

Depending on the nature of the histological study in question, the field can be broken down into a number of different descriptive subdivisions. Histochemistry refers to the examination of tissue’s chemical composition, histophysiology covers the studies of all different physiological processes, and developmental histology refers to different forms of tissue growth in developing embryos.

The Process of Fixation

In order to preserve the tissue against decomposition during the sample preparation phase, histologists will apply a special chemical fixative. In addition to keeping the cell tissue from degrading, the chemical fixative will also help to keep the structure of the cell and all of its smaller components securely formed on a fundamental level. Certain fixatives are capable of preserving the tissue they’re applied to from degrading by the way of protein crosslinking.

Under certain circumstances, a histologist will make use of a special refrigeration device that is referred to as a cryostat; this is known as the process of frozen section fixation, which is employed when the process calls for the mounting of histology sections. With frozen section fixation, the determination of margin can be accelerated following the complete removal of a tumor.

Sample Processing and Embedding

Before the sample can be considered fully prepared, it needs to be processed and embedded properly. With processing, the aim is to ensure that all excess hydration within the tissue can be replaced with a solution that allows small slivers to be sliced and arranged. Once all of the excess hydration has been removed, the sample can be cleared for the embedding process. Different molds serve as receptacles for the dehydrated tissues, in which they await sectioning and staining.


The anatomy of every single plant and animal on the planet can have the histological process applied to understand it more thoroughly. Histological staining has become one of the most fundamental research methods employed in all different areas of biomedical practice.