The behaviour of colloids dispersed in a phase-separating microemulsion (micellar solution) is explored using microscopy techniques. It is well known that the colloids will cluster approaching a demixing transition of the host solvent [1] when this is poor in the preferred phase; the mechanism is still unresolved. Here we choose a system that is intrinsically slow, facilitating experimental study by direct imaging. The microemulsion is composed of sodium dodecyl sulphate, dodecane, pentanol, and water [2]. The colloids (530 nm radius) are sterically stabilized poly(methyl methacrylate). On raising the temperature the pure microemulsion separates into micellar liquid and micellar gas phases. The gas phase contains a smaller proportion of the micelles and is less dense. The dynamics are slow, partly because of the size of the micelles (5-9 nm diameter). Well before demixing of the microemulsion that has composition range that is poor in the component preferred by the colloids (micellar gas), clustering of the colloids is observed: initially the clusters are irregular in shape and continuously aggregate. When the system gets closer to the phase boundary a wetting layer of the gas phase becomes visible around the colloidal aggregates; at around this temperature the shape changes from irregular to spherical. These stages (Fig. 1) have never previously been imaged directly. Following complete phase separation the colloids prefer the micellar gas phase. The colloidal clusters originating prior to demixing cream to the top of the container. Some colloids fall out of the droplets while it is moving giving the appearance of colloidal comets. In the microemulsion composition range that is rich in the component preferred by the colloids (micellar gas) initially micellar liquid phase nucleates while the colloids remain in the preferred micellar gas phase, and the droplets grow slowly until these fill up nearly all space (Fig 2). This late stage phase separation behaviour is reminiscent of viscoelastic phase separation observed in polymer systems [3]. Figure 1: The various stages observed prior to and during phase separation (scale bar = 100 micron). Figure 2: The increasing colloid concentration in the remaining gas phase appears to greatly hinder coalescence. Eventually the interface breaks (scale bar = 100 micron). [1] D. Beysens and D. Estève, Phys. Rev. Lett. 54, 2123 (1985). [2] A. M. Bellocq and D. Roux, Microemulsions: Structure and dynamics, ed. S. Friberg and P. Bothorel (CRC Press, F1, 1987) [3] H. Tanaka, J. Phys.: Condens. Matter 12, R207 (2000)