These are cells, extracellular substances, and body fluids. Individual materials can be seen and localised by histochemistry.
Fixation stabilizes mainly proteins, and protein conjugates.
These substances are used as building materials for the firmer structures of the cell. Lipids, minerals, glucose, and smaller molecules are usually lost from the section during processing. During development from the fertilized oocyte, a great variety of cells is formed in the mammal, each kind specializing in a certain function, e.g., secretion, but many activities, such as energy production, are common to all cells. Cell morphology Cells performing a given function have a characteristic size, form and fine structure adapted to that task. However it may help at this stage to think in terms of a composite cell having all the features the various cells of the body display.