Oil loading in aqueous formulations is a constant challenge when developing cosmetics with new claims, and different parameters may affect their preparation and properties. For instance, several methods require high energy input or are not adaptable to large-scale production in an industrial context. If nanoparticles with a high amount of oil loading are desired, this becomes even more challenging. Formulating with chemicals already used in cosmetics or using biocompatible ones is also essential. A possible strategy to avoid these issues involves using poly(ethylene oxide)-poly(propylene oxide)- poly(ethylene oxide) (EOxPOyEOx), which are already approved for cosmetics and pharmaceutical formulations, their availability in different chain lengths and proportions of EO/PO groups can allow the control of different properties, such as enhancing stability in an aqueous medium by increasing the EO chain length. This thesis aims to design, obtain, and characterize different colloids, in four different papers, using triblock copolymers to uptake hydrophobic ingredients in aqueous formulations. By employing simple preparation methods, we explore a range of colloidal structures, from nanoparticles to microcapsules, aiming to understand how the copolymer’s structure influences the final properties. These methods included spontaneous capsule formation through charge-driven complexation to the use of copolymers to stabilize liquid crystals dispersions. In the first study, core-shell particles were obtained through complexation between oxidized cellulose nanofibrils (OCNF) and poly(diallyldimethylammonium chloride) (PDADMAC), with triblock copolymers enhancing stability and oil loading. This method resulted in stable particles with high oil incorporation capacity, suitable for controlled release of active ingredients. In the second study, dispersing lamellar phases formed by sodium lauryl sulfate (SDS) and fatty alcohols using triblock copolymers enabled the formation of nanoparticles with water like viscosity and high stability, suitable for products with light textures. The third study utilized complexation between oppositely charged surfactants and polymers to form nanoparticles with high oil loading capacity, where the triblock copolymer improved stability and loading efficiency. Finally, the fourth study explored the use of cocamidopropyl betaine as a surfactant, forming micelles that can be used in personal care formulations. The results highlight the potential of these systems for applications in cosmetic products, where stability and active ingredient incorporation are essential.