The endosymbiotic theory, first proposed by Lynn Margulis, states that primitive microorganisms once fed between them, which eventually led to the origin of superior organisms, such as eukaryotes, which is supported by the evidence that cell organelles such as mitochondria, and the endoplasmic reticulum represents, that have a double membrane and synthetizes such important molecules for the survival of the cell, as are ATP, lipids, and proteins.