What material had Robert Hooke used …

Discovery of Cell:

While examining a thin slice of cork, Robert Hooke saw that the cork resembled the structure of a honeycomb consisting of many little compartments. Cork is a substance which comes from the bark of a tree. In the year 1665, Robert Hooke made this chance observation through a self-designed microscope. Robert Hooke called these boxes cells. Cell is a Latin word for ‘a little room’.

Thus, cells were first discovered by Robert Hooke  in 1665. He observed the cells in a cork slice with the help of a primitive microscope. Leeuwenhoek (1674), with the improved microscope, discovered the free living cells in pond water for the first time.  Robert Brown in 1831 discovered the nucleus in the cell.  Purkinje in 1839 coined the term ‘protoplasm’ for the fluid substance of the cell. The cell theory was presented by two biologists, Schleiden (1838) and Schwann (1839). This theory states that all the plants and animals are composed of cells and that the cell is the basic unit of life. The cell theory was further expanded by Virchow (1855) by suggesting that all cells arise from pre-existing cells.