Structure of a granum (IMAGE) Eötvös Loránd University Caption Structure of a granum (star) in an electron microscope (left, green arrow: envelope membrane, white arrow: stromal thylakoid) and a model demonstrating the repeat distance (basic unit of the granum) Credit Photo: Eötvös Loránd University Usage Restrictions Credit must be given License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.