Cell is the basic unit of life. The structural and functional unit of life is called cell. Our body is made up of billions of cells.
English scientist, Robert Hooke examining a thin slice of cork under a microscope, found that it consisted of many neatly arranged small honeycomb like structures. He named them cells. Those were dead cells. Living cells contain protoplasm. In fact, during his experiment Robert Hook could only see the walls around those cells.
Types of cell
On the basis of the presence or absence of nucleus, cells can mainly be divided into two types; proto cell and eucell.
The nucleus is not well developed in proto cells and the nuclear membrane is absent, example: bacteria.
In eucell the nucleus is well developed and surrounded by nuclear membranes. Depending on their functions, the eucell can again be divided into two groups: somatic cells and reproductive cells.
Somatic cells take part in growth and development of our body structure. Due to the cell division the organisms grow. Reproductive cells take pan in reproduction. Many different forms of cells are found in living organisms. It is natural to find difference in the shapes and sizes of cells. Different shapes of cells include round, oval, rectangular, etc. Generally, cells are so small that they cannot be seen with naked eyes.