PACS. 64.70Pf -Glass transitions. PACS. 61.20Lc -Time-dependent properties; relaxation.Abstract. -We study the aging of a colloidal glass, which is obtained for extremely low volume fractions due to strong electrostatic repulsions, leading to the formation of a "Wigner glass". During the aging, a new crossover between a complete and incomplete decay of the correlation function is observed, accompanied by an increase in the non-ergodicity parameter. The dynamics can be described as a cage-diffusion process. For short times, the escape of the particles from "cages" formed by neighbouring particles dominates; for long times the particles cannot escape anymore and the system becomes strongly non-ergodic.Glasses are a non-equilibrium form of matter and are, maybe for that reason, still illunderstood [1][2][3][4]. The usual way of looking at the glass transition is given by the so-called schematic mode-coupling theory [1,2]. In this theory, the glass transition is a strong ergodic to non-ergodic transition. In real systems, however, the "transition" always appears rounded. The rounding of the transition is due to the appearance of a "slow mode" in the system [1-4]. The non-equilibrium evolution of a system quenched into a glassy state is often referred to as aging, and is common to both structural and spin-glasses. Understanding the aging processes in a glassy system is crucial for the description of glassy dynamics; unfortunately, due to its very nature, the classical mode-coupling theory does not provide us with any information on the aging process [2].A recent careful inspection of the mode-coupling equations [4] reveals that this serious limitation may in fact be overcome. This work presents the first detailed description of the aging process. The evolution of the system is described in terms of the correlation and response functions of the system. Unfortunately, for most of the systems (structural glasses) studied to date, these quantities are not easy to obtain experimentally. For this reason, progress has been limited to a number of recent theoretical (spin-glass) and simulation (Lennard-Jones glass) studies [3,4]. The key result of both theory and simulations is that the diffusion may be looked upon as a cage-diffusion process. The particles reside in dynamic cages formed by c EDP Sciences