[Cellular and molecular motions: order and disorder]

Video-microscopy allows monitoring the dynamics of biological components, specifically labeled, usually by fluorescent tags such as GFP or quantum dots, either at the cellular or at the molecular scale. Reconstructing trajectories over time with dedicated algorithms allows to characterize on both scale different categories of movement, such as random, linear or confined, and to report events such as transient confinements among recorded species and with their environment. Single cell or molecule measurements hence provide detailed access not only to mean values of relevant descriptors, such as speed or interaction duration, but also to the exhaustive distribution of recorded values.