It is also known as Endoskeleton of the cell, Endomembranous system of the cell.
Garnier (1897) first observed them and called Ergastoplasm.
E.R. name proposed by Porter (1961).
E.R. present in all eukaryotic cells.
E.R. is a diffused cell organelle.
E.R. consists of three structure :-
(1) Cisternae - Long flattened and unbranched units arranged in stacks. 40-50 nm thick.
(2) Vesicles - 25-500 nm in diameter.
(3) Tubules - Long, isolated, branched units. 50-190 nm thick
Structure of E.R. is like the golgi body but in E.R. cisternae, vesicles and tubules are isolated in cytoplasm and these do not form complex.
Golgi body is localised cell organelle while E.R. is widespread in cytoplasm.