In the new paradigms of regenerative medicine, the use of biomaterials in contact with biological material (e.g., cells, tissues/organs, physiological fluids, biomolecules) is a current illustration of the need of interdisciplinary scientific approaches that combine the most recent advances in materials science and technology, basic sciences, and life sciences. In tissue engineering (TE), matrices are developed to support cells, promoting their differentiation and proliferation toward the formation of new tissue. Such strategies allow the fabrication of hybrid constructs that can be implantable in patients to induce the regeneration of tissues or replace failing or malfunctioning organs. Different materials have been proposed to be used in the processing of scaffolds, namely biodegradable polymers. Natural-based polymers offer the advantage of being similar to biological macromolecules, which the biological environment is prepared to recognize and to deal with metabolically. Due to their similarity with the extracellular matrix (ECM), natural polymers may also avoid the stimulation of chronic inflammation or immunological reactions and toxicity, often detected with synthetic polymers. In this chapter, the different natural-based materials that have been proposed to be used in TE strategies will be overviewed. An important aspect, also addressed, is the processing of such kind of materials into porous matrices, a task that usually needs other technologies than those usually employed in the processing of conventional synthetic polymers. There is also a clinical need for processing biomaterials into other shapes, including nano-/microparticles (for control release application). Materials containing cells and bioactive agents that can be implanted in a noninvasive way are very attractive approaches in TE and regeneration contexts, which will be also discussed.