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.

You may have seen masons building a brick wall. How many bricks are needed to build a wall? You will say that a huge number of bricks will be needed. In fact, numerous bricks are stocked together to make a wall. In this way, gradually, a big building is built. After the building is constructed, you cannot separate one brick from the other. Before erecting the building, everyone would call brick and now they are calling it a building house, aren’t they? Your body, my body and all bodies are made up of many such brick-shaped small boxes. Now, these boxes are known as cells to us.

Amoeba or chlorella is made up of only one cell. Do you know who discovered cells? In 1665, an English scientist, Robert Hooke, while 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