A. Group of cells
Cells - Tissue - Organ ...
If you want to know more - look for "Biological Organisation"
Some samples are transparent, or very difficult to see, therefore, they are stained in order to be seen more clearly and easier to work with.
During eye surgery, the clear layer of the eye is stained to be easily extracted, if it was clear then the surgeon might cut the eye instead of just the layer.
Hope this helps, u might want to search online for more info.
Diffusion<span> is a spontaneous movement of particles from an area of high concentration to an area of low concentration. ... </span>Osmosis<span> is the spontaneous net movement of water across a semipermeable membrane from a region of low solute concentration to a more concentrated solution, up a concentration gradient.
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