In 1838 the cell theory was proposed by two German scientists Schleiden and Schwann.
It describes the basic concept of how life on Earth functions .
The principles of cell theory are:
- All the living organisms are composed of cells .
- The living organisms could be made up of one or more cells .
- The new cells arise from pre-existing cells through the process of cell division .
- The cells in different organisms vary in the number, shape and size .