Cell fractionation is the separation of homogeneous sets from a larger population of cells.
Tissue is typically homogenized in an isotonic buffer solution, as well as a pH buffer by use of a variety of mechanisms such as grinding, mincing, chopping, pressure changes, osmotic shock, freeze-thawing, and ultra-sound homogenization. This is done to stop osmotic damage. The samples are then kept cold to prevent enzymatic damage .
This step may not be necessary depending on the source of the cells. Animal tissue however is likely to yield connective tissue which must be removed. Commonly, filtration is achieved either by pouring through gauze or with a suction filter and the relevant grade ceramic filter.
Invariably achieved by Differential centrifugation - the sequential increase in gravitational force results in the sequential separation of organelles according to their density.
Media for cell separation by density: