Cytology is the science of studying cells; cyto “cell” + ology “science of or studying”. Cyto is derived from the Greek word kytos meaning a basket. The term cell biology is more or less equivalent to cytology. Both cytology and cell biology refer to the science of studying cell structure and function including cell division.

There are two main classes of cells: eukaryotic cells and prokaryotic cells. The main difference between the two is that prokaryotic cells lack a nucleus. They also lack membranous cytoplasmic organelles and are often smaller than eukaryotic cells. Prokaryotic bacteria and Arkaea – a primitive form of living organisms.