Multifunctional materials and devices with captivating properties can be assembled from cellulose and cellulose-based composite materials combining functionality with structural performance. Cellulose is one of the most abundant renewable materials with captivating properties, such as mechanical robustness, biocompatibility, and biodegradability. Cellulose is a low-cost and abundant biodegradable resource, CO₂ neutral, with a wide variety of fibers available all over the world. Over thousands of years, nature has perfected cellulose-based materials according to their needs, such as function vs. structure. Mimicking molecular structures at the nano-, micro-, and macroscales existing in nature is a great strategy to produce synthetic cellulose-based active materials. A concise background of cellulose and its structural organization, as well as the nomenclature of cellulose nanomaterials, are first addressed. Key examples of nature-designed materials with unique characteristics, such as “eternal” coloration and water-induced movement are presented. The production of biomimetic fiber and 2D fiber-based cellulosic materials that have attracted significant attention within the scientific community are represented. Nature-inspired materials with a focus on functionality and response to an external stimulus are reported. Some examples of 3D-printed cellulosic materials bioinspired, reported recently in the literature, are addressed. Finally, printed cellulosic materials that morph from a 1D strand or 2D surface into a 3D shape, in response to an external stimulus, are reported. The purpose of this review is to discuss the most recent developments in the field of “nature-inspired” cellulose-based active materials regarding design, manufacturing, and inspirational sources that feature existing tendencies.