**1. Introduction**

Every year, hundred billion tons of cellulose are produced by nature from various biomass sources, making this biopolymer an ultimate platform for developing sustainable applications on an industrial scale [1]. The increased environmental awareness due to global climate changes has pushed cellulose science to advance rapidly, and thus cellulose is expected to continue playing a central role in the emergent bio-economies and biorefineries. Cellulose extraction and purification rely on fairly simple, scalable, and efficient isolation techniques, and cellulose can be further modified and shaped into different colloidal and macroscopic forms, showing very different features [2–5].

Emulsions are among the most important colloids in everyday life, and have multiple uses, from technical applications, such as paints and coatings, to life science applications, such as foods, pharmaceuticals, and cosmetics. Emulsions can encapsulate and protect sensitive ingredients, adjust appearance, taste and sensorial properties, and facilitate application, spreading and drying. They can also serve as an intermediator for efficient oil extraction, polymerization reactions, and the production of microcapsules and lightweight foams [6]. Their structural and

functional properties are vast and therefore, the emulsifiers and stabilizers must be carefully selected according to the needs. With the growing global demand for sustainable and "clean-label" products, industries are actively seeking to replace synthetic emulsifiers by new alternatives. Finding natural ingredients, with minimal modification requirements (without compromising environment and human health) and still being capable of achieving a competitive performance to the optimized synthetic options is highly desirable but challenging. In this respect, cellulose has the potential to become a key star player in emulsion systems. In addition to its natural, non-toxic, biodegradable, and renewable nature, it is also a versatile source of natural emulsifiers. From cellulose derivatives, used since the early 20th century, to the more recently explored native forms of cellulose, including nanocelluloses, and the native cellulose itself, either molecular or in the form of polymeric particles and microgels, all its different morphological forms have shown an intrinsic amphiphilic character by self-assembling at oil–water interfaces.
