The greening process in etiolated fig leaves (Ficus cayica L.) upon illumination with respect to the change of chloroplast ultrastructure and plastid nucleoids (pt-nucleoids) was studied with optical and transmission electron microscopy. With enlarging leaf size on the different nodal positions under dark conditions there were typical changes in the mesophyll including plastid morphology and synthesis of the lamellar system. Much of the starch disappeared, while rapid membrane synthesis resulted in an extensive prolamellar body formed in the plastid in the dark. During greening in the light after being transferred from dark conditions, leaf area, palisade parenchyma cells and intercellular spaces developed rapidly. The prolamellar body disappeared immediately after illumination. Increased membrane appression in chloroplasts was indicative of illumination, although overlaps had already begun to form in the dark. Changes in pt-nucleoids in etiolated fig leaves or during greening were followed by fluorescence microscopy after staining with DAPI (4′, 6-diamidino-2-phenylindole). Relatively large pt-nucleoids were first located in the plastids in the etiolated younger leaf, then daughter pt-nucleoids divided off and separated from these larger pt-nucleoids with development of the plastid. Upon illumination, pt-nucleoids were more separated from each other and were distributed evenly in the chloroplast, suggesting a relationship between formation of the thylakoid system and the behavior of pt-nucleoids.