Cell and The Light Microscope

By the end of the nineteenth century, most of the structures visible with a light microscope had been discovered.

A light microscope is one that uses light as a source of radiation.

The cell can be described as a small unit of living protoplasm, always surrounded by a cell surface membrane and sometimes, as in the case of plants, by a non-living wall.

The most conspicuous structure in the cell is the nucleus, which contains a deeply staining material known as chromatin (meaning colored material).

This is the loosely coiled form of chromosomes. Chromosomes appear as thread-like structures just before nuclear division.

They contain DNA, the genetic material, DNA controls the cell's activities and can replicate itself so that new cells can form.

The living material between the nucleus and the cell surface membrane is known as cytoplasm. This contains a variety of organelles.

An organelle is a distinct part of a cell that has a particular structure and function. 

The only organelle found in animal cells that is absent from plant cells is the centriole.