A cell is the smallest structural and functional unit of living organisms. Cells are building blocks of living organisms; they make the structure of the living organisms. Cell can carry out all life processes that is respiration, reproduction etc. cells were discovered in 1665 by Robert Hooke.

A living organism can either be multi-cellular or unicellular. Multi-cellular organisms are made up of many cells e.g. plants, animals, man. While unicellular organisms are made up of one cell e.g. bacteria, amoeba etc.