Nanocellulose aerogels are lightweight, open-porous solids prepared from nanocellulose hydrogels through methods, replacing the continuous fluid gel phase by air at far-reaching preservation of their original architecture. Intriguingly, the morphology and properties of nanocellulose aerogels can be tuned across a broad range, depending on the choice of nanocellulose building blocks used in gel formation. All of them have in common to self-assemble in aqueous dispersion state, leading to different liquid-crystalline arrangements and network morphologies, which can impart directional properties to aerogels. The latter can be used in advanced applications such as heat and sound conduction, light and gas transmission, or photonic platforms. This chapter offers a brief introduction to the captivating world of nanocellulose aerogels, covering their preparation, potential reinforcement, and surface modification strategies. It also highlights their extensive application potential, such as in thermal superinsulation, passive daytime radiative cooling, atmospheric water harvesting, selective sorption, removal of pollutants from air and water, plasmonic devices, or controlled release of bioactive compounds.