**Preface to "Advances in Cellulose-Based Hydrogels"**

Cellulose is the most abundant natural biopolymer on Earth. With an estimated annual production of 1.5 x 10<sup>12</sup> tons globally, and the possibility of its extraction even from waste sources, it is considered an almost inexhaustible source of raw material capable to make up for the growing demand for environmentally friendly and biocompatible products. Within this framework, cellulose-based hydrogels usually combine hydrophilicity, biodegradability, non-toxicity, and biocompatibility together with low costs and massive availability, which make them extremely attractive in both academic and industrial fields. Possible application fields include biomedical engineering (e.g., tissue engineering and regenerative medicine, drug/cell delivery systems, and 3D printing and bioprinting), progress in smart systems (e.g., sensors, actuators, and soft robotics) and stimuli-responsive systems (e.g., pH- or thermo-responsive hydrogels), the agricultural sector (e.g., soil conditioning, nutrient carriers, and water reservoirs), and water purification.

This volume collects the recent progress in cellulose-based hydrogels, including gels prepared from natural cellulose and its derivatives, cellulose graft co-polymers, and composite gels based on cellulose, covering key aspects of cellulose-based hydrogels, including design, characterization, as well as application-focused research.

We want to deeply thank all contributing authors whose expert contributions made the publication of this Special Issue possible. We would also like to express our deepest appreciation to the editorial team, especially Ms. Miranda Song at MDPI for her encouragement, technical guidance, editing, and publication of this Special Issue.

> **Christian Demitri, Lorenzo Bonetti, and Laura Riva** *Editors*
