In the next web pages about histological techniques we are going to explain the methodology to obtain animal and plant tissue sections, stained and ready to be observed with a microscope. So, there are sections dealing with getting the samples, fixation, embedding, obtaining sections, and staining. The instruments to manipulate the samples are also introduced, highlighting what they are useful for but not explained in detail how they operate. There are a sections about protocols and recipes of the more common techiques and solutions, and some videos are also included.
Most of the histological techiques are performed to obtain tissue sections to be studied under either light or electron microscope. Except some cases, sections need to be stained (or contrasted) to observe and differentiate all their structures. These techniques include a previous fixation of the tissues to prevent the natural degradation and chemical compounds (mostly dyes) to observe the morphological and chemical features of the tissue.
There are quick and simple procedures to study live tissues and cells, known as vital. Intravital techniques allow the observation of tissues and cells in the body. For example, the study of the blood flow inside the blood vessels. More complex are the supravital techniques, that allow the study of tissues and cells that have been removed from the body and kept alive in the laboratory. For example, cell and tissue cultures. In these procedures, dyes that do no kill the cells can be used to stain tissues. They are the so-called vital dyes.
Postvital histological techniques entail the dead of the cells, but the morphological and molecular features of the live tissue are preserved as much as possible, which depends on the type of histological procedure. The following web pages in this section are dealing with postvital techiques because they are the most common techiques in histology laboratories.