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Steps to prepare a tissue:
Chemical fixation: A chemical fixative is added that kills the cells and stop chemical reactions. A most crucial chemical reactions would digest the cell itself is a process called "autolysis."
Embedding in substance then cutted (sectioning): After being fixed, it's embedded in something that makes it rigid enough to be cut by a microtome - as to why steaks are put in fridges before being sliced in a recipe.
How things are sectioned have profound effects on how they actually look on a slide.
E.g. With a simple object, an egg and a transparent egg:
Imagine that the white is a cell's cytoplasm
and the yolk is the nucleus.
How we see the egg on a slide depend on the angle the section was cut. Imagine 2 cuts on the left, sagittal sections through the egg, right in the center of the eggs.
If it's turned 90 degrees, the section on the right is how the egg look in a slide.
With a coronal section, it's the exact same thing: slicing the egg two cuts and turned 90 degrees, on to the slide, the cytoplasm and yolk of the egg are seen.
But if cutting it slightly off the center (roughly 1/3) in the transparent egg, through the white and the yoke but not through the yolk's center, a nucleolus may be missed.
It wouldn't look like the previous version
If it's slightly off the center and we do
what's called (in histology) a "grazing section,"
there will be less of the yolk, more of the white, a smaller part of the cell and again, it won't look like the first version.
And finally, if we just do an axial section of the tip of the cell, that is all we'll see on the slide.
And that's a reason why all cell on a tissue side won't be identifiable as something that you recognized and why all the features you expect to find in a cell may have been left out in another section.
After sectioning, we'll have a thin colorless slice of tissue.
To bring it into some form where the tissues can be seen: Stain with 2 stains, a bright stain and a counter stain.
Due to their chemical properties, the stains will pick up the cell's features.
"Hematoxylin" is a basic dye, which will bind to acidic cell components and stain them purple or dark blue.
E.g. of things stain purple and blue using hematoxylin is DNA and RNA in a nucleus, other carbohydrates.
"Eosin" is an acidic stain, which binds to basic cell components.
Cytoplasm filaments, the plasma membrane, collagen fibers outside a cell will stain things orangy pink.
The nucleus will be purple with many DNA.
The nucleolus will be dark purple with many RNA synthesis.
Then the basic cell components, the dye, will bind to them.
So these cell's features are pink and again the cytoplasm.
Hematoxylin staining acidic components blue.
Eosin staining almost all else pink.
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