Question

who gave cell theory define it

Answer 1

Cell theory was given by M. J. Schleidin and Schwann
According to this all organisms are made up of cells
it was later give by Rudolf Virchow
he said that all cells arise from pre existing cells

Answer 2

this theory was given by Theodor Schwann, Matthais Schleiden and Rudolph Virchow.
This theory states that all living organisms are composed of cells. They may be unicellular or multicellular.