The combined observations and conclusions of cell biologists over many years led to the development of the cell theory, which states:
-All living things are composed of cells.
-Cells are the basic units of structure and function in living things.
-All cells come from preexisting cells.
Schlerden and Schawn came up with this theory in 1938 and 1939. A virus is not consider a living organism because is not made out of cells. A virus is a fragment of DNA or RNA which is sorrunded by a protein coat. Virus are the smallest living/nonliving structures ( 20 to 300nm ). They are consider as parasiters because they need hosts in orther to reproduce.
There are two types of microscopes which are: light and electron microscopes. The light microscope is cheap and can be used to observe living material, (movement), but it has a poor resolution and magnification. The electron microscope is very expensive and you cannot observe living material in it, but it has a high resolution and magnification.
Microscopes: 1mm = 1000 micrones = 1000000 nanometers (nm)
