Organisms differ from each other structurally and functionally but all are made up of cells.
All living organisms carry out certain basic functions.
The basic structural and functional unit of an organ is the cell.
Discovery of the cell:
Robert Hooke in 1665 observed slices of cork under a simple magnifying device. Cork is a substance which comes from the bark of a tree. He noticed partitioned boxes or compartments in the cork slice. These boxes appeared like a honeycomb. Each box was separated from the other by a wall.