Microscopic View of the Thymus (IMAGE) Walter and Eliza Hall Institute Caption Microscopic view of cells in the thymus, an organ located just above the heart that trains immune T cells to defend the body against viruses and bacteria. Credit Walter and Eliza Hall Institute, Australia Usage Restrictions With credit License Licensed 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.