Nanocellulose in its various forms has recently been hatched as an innovative material for engineering the next generation of integrated, flexible, and sustainable optical devices. This is mostly due to the possibility of forming ordered structures such as Bragg stacks and chiral nematic crystals. Recent studies leveraged the formation of cellulose nano- and microstructures toward soft sensors, colored appearance, display, and energy harvesting. In this spotlight, an up-to-date account of recently selected advances in this domain is given. Our discussion includes basic mechanistic principles and design strategies based thereon that are essential for unlocking fresh perspectives for biomimetic materials with optical functionality. We also discuss possibilities from the combination of structured cellulose nanomaterials with a secondary optically functional entity, such as plasmonic or excitonic nanoparticles, and how this combination can broaden the scope regarding more sophisticated application scenarios. It is our hope that this review will promote the development of cellulose nanomaterial-based optics in the context of sustainability.