In tissue engineering, neo-organ is the final structure of a procedure based on transplantation consisting of endogenous stem/progenitor cells grown ex vivo within predesigned matrix scaffolds. Current organ donation faces the problems of patients waiting to match for an organ and the possible risk of the patient's body rejecting the organ. Neo-organs are being researched as a solution to those problems with organ donation. Suitable methods for creating neo-organs are still under development. One experimental method is using adult stem cells, which use the patients own stem cells for organ donation. Currently this method can be combined with decellularization, which uses a donor organ for structural support but removes the donors cells from the organ. Similarly, the concept of 3-D bioprinting organs has shown experimental success in printing bioink layers that mimic the layer of organ tissues. However, these bioinks do not provide structural support like a donor organ. Current methods of clinically successful neo-organs use a combination of decellularized donor organs, along with adult stem cells of the organ recipient to account for both the structural support of a donor organ and the personalization of the organ for each individual patient to reduce the chance of rejection. Background The word neo-organ comes from the Greek word "neos," which means new. Organ transplants have been successfully used for medical purposes since 1954. The difficulty with the traditional process of organ transplants is that it requires waiting for a viable donor to donate an organ. The process of matching the organ to make sure it is compatible with the patient has also proven to be challenging. There are two main challenges: finding the right candidate for the patient and avoiding the patient rejecting the organ even if it is a match. Neo-organs can be used to avoid the process of organ matching and donating. Neo-Organ Creation Methods Research is being conducted for methods of creating neo-organs including three methods such as using adult stem cells, decellularization, and 3-D Bioprinting: Adult Stem Cells One of the most studied methods is to use the patients own cells to generate a new organ, ex-vivo Specifically, researchers have chosen to focus on adult stem cells, or somatic stem cells, for the generation of new organ cells to create organs. There has been success in the production and use of some organs. The first stem-cell based organ, a tracheal graft, was transplanted successfully in 2008. The