Speckle Pattern in Unclotted Whole Blood (video) The Optical Society Loading video... Caption This video shows the rapid "twinkling" or intensity fluctuations of the speckle pattern in a drop of unclotted whole blood. The rapid "twinkling" is due to the fast thermally-driven motion of blood cells that scatter light. Credit Seemantini Nadkarni Usage Restrictions None 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.