Newly produced secretory insulin granules are secreted preferentially and are more mobile than their older counterparts. The mechanisms that are responsible for these different nobilities and the tendency for exocytosis of secretory granules of differing ages were unknown up to now. A very recent investigation has shown that the aged secretory granules exhibit a reduced competence for glucose-stimulated, microtubule-mediated transport. These new results should help us to better understand insulin secretion in healthy subjects and diabetic patients.