###### Abstract
ECM consists of a large variety of fibrillar macromolecules including collagens, laminins, elastin, fibronectin, glycoproteins, proteoglycans, and glycosaminoglycans that form the major structural components of ECM. In addition,all cell types synthesize and secrete matrix macromolecules, growth factors, cytokines, and other signaling molecules and result in ECMs that are unique to each tissue and organ in the body. New discoveries about ECM composition and function continue to be made, and this wealth of knowledge has allowed researchers to utilize components of ECM to engineer scaffold to attract cells and promote cell growth or differentiation. Others have used the native ECM, derived from decellularized tissues, as nature's ideal biological scaffold material to promote site-appropriate tissue repair and potentially grow new tissues and organs in vitro. In this Special Issue, [PERSON] et al. provide a review of the use of decellularized scaffolds for skin repair and regeneration [1]. This provides an excellent introduction to the topic and describes in detail the different source tissue from which the scaffold materials are derived and the different techniques that can be used to successfully remove cells from tissue. The article highlights the diversity of decellularized scaffolds that are now in clinical use, showing that it is not necessary to use a tissue-specific scaffold material to promote constructive tissue remodeling and that scaffold materials derived from intestine, bladder or amniotic membrane are equally practical for promoting skin wound repair. In their review of whole organ engineering, [PERSON] et al. describe how the decellularization techniques described by [PERSON] et al. have been adapted and applied to the field of organ transplantation to develop decellularized organs with the long-term goal of having \"off the shelf\" organ transplants available for patients [2]. This comprehensive review describes the long history of tissue engineering and longstanding goal to develop functional organs in vitro. The review article highlights the important steps in cell culture, scaffold development, and surgical technique that have allowed advances in organ engineering to take place. The article describes the different potential approaches to using ECM for organ engineering, from using decellularized cadaveric organs to using engineered ECM scaffolds such as films or sponges through to more modern approaches such as 3D printing of ECM gels. Importantly, in addition to highlighting the advances that have been made, [PERSON] et al. also discuss the challenges and barriers to market that still need to be overcome. These are challenges that not only affect whole organ engineering but are limiting factors to translating all ECM-based regenerative medicine strategies into therapeutic products. In addition to ECM scaffolds derived from decellularized tissues, researchers also use components of ECM to manufacture novel scaffold materials for regenerative medicine, and several examples are included in this Special Issue. [PERSON] et al. describe their work fabricating engineered scaffolds from collagen and fibronectin [3]. In this study, the authors expose the collagen and fibronectin gels to ultrasound waves during the polymerization phase. This results in a distinct pattern of collagen fibril formation and closer association of the fibronectin component to the collagen fibrils. While the ultrasound-treated gels reduced initial cell attachment, they promoted the formation of more multicellular spheroids, and refinement of this technique could result in scaffolds with defined ECM structures that could promote specific cell behaviors. The paper by [PERSON] and [PERSON] also focuses on the development of an engineered ECM scaffold, in this case a hybrid scaffold combining chitosan with an ECM hydrogel derived from decellularized urinary bladder [4]. In this study, the authors show that by varying the proportions of the chitosan and ECM gels, they can produce scaffolds with different physical properties.