ORGANELLE DIAGRAM: ROUGH ENDOPLASMIC RETICULUM or RER:
In this picture, the rough endoplasmic reticulum is seen as stack of golden cisternae connected by bridges. It is sectioned to reveal the interior space or "lumen" which appears purple. At lower left, the lumen is seen to be continuous with the lumen of the nuclear envelope. The surface (golden) is covered by ribosomes, which impart the "rough" appearance. Proteins synthesised by these attached ribosomes pass into the lumen. At upper right, small transitional vesicles can be seen budding from the roughER. These carry proteins destined for processing by the Golgi.
As well as connecting to the nuclear envelope, the rough ER is continuous with the smooth endoplasmic reticulum.