Most cosmetic formulations are composed of various substances including water, oils and other moisturizing ingredients, active agents (anti-wrinkle, antioxidant, makeup, sunlight protection, cleansing), preservatives, perfumes, and texturing agents with specific functions. Such complex multiphase systems are conventionally stabilized by surfactant molecules, which may cause irritancy or other adverse reactions to the skin. Current trends in cosmetics, driven by the increasing demands of more informed and awareness among consumers and stricter regulations, include more sustainable, natural, and vegan formulations, non-irritant or skin sensitizing ingredients, and substitutes for ionic surfactants (Bianchet et al., Biotechnol Rep 27:e00502, 2020; Bom et al., J Clean Prod 225:270–290, 2019; Tournilhac and Lorant, Espec. Cosmet. Uses 1(12), 2003)). Oil-in-water emulsions are more frequent in the cosmetic field because water as the external phase provides a cooler, less greasy, and lighter feel when applied to the skin. Besides function, stability, and organoleptic properties of these products, shear-thinning behavior and particle suspension capabilities are among the desired properties of many cosmetic emulsions. The suspended materials can be functional (exfoliants, oils, encapsulates, and active agents) or simply aesthetic, and the shear-thinning response improves the spreadability and facilitates rubbing of the product on the skin. In this scope, natural solid particles—particularly BC—emerge as promising stabilizers and rheology modifiers for the production of green and safe cosmetic emulsions, a topic addressed in this chapter, including applications in other multiphasic systems (solid dispersions in liquids and foams).