Reversible aggregation of colloids is known to exhibit various intriguing phenomena, such as transient gel formation, compaction, and crystallization. A reversible aggregation process can be induced by creating a depletion interaction that originates when a non-adsorbing polymer is added to an otherwise stable colloidal solution. A major advantage of the depletion-driven systems is that the strength and range of the depletion interaction can be easily controlled by varying the polymer concentration and the length of the added polymer chains. In this talk we present and discuss results from detailed numerical Brownian dynamics simulations in a two-dimensional depletion-driven colloidal system.