It is often called as the building block of life. The term cell comes from a Latin word cella which means small room. This term was used in Robert Hooke’s book in 1665.
Living organisms can be classified according to cells. A unicellular organism like most of the bacteria has a single cell. A multicellular organism like plants and animals has numerous cells. A human has about 100 trillion cells and each cell is 1-100 micrometres small which can only be seen though a microscope.
There are two types of cells.
Prokaryotic cells- simpler, smaller lack nucleus and most organelles of eukaryotes
Eukaryotic cells- about 15 times wider and 1000 times greater than prokaryotic, contain membranes where metabolic functions take place