**6. Future perspective of 3D culture, organoid models in COVID research**

In its earliest phases, the creation of 3D organoid products from human PSCs has now advanced rapidly. Soon human organoids can be produced for organisms already developed in the mouse or when re-aggregation investigations have already demonstrated a source of self-orientation. The skin, mammary gland, muscle and bone are part of it [27]. Organ expansion models since organoids show a model approach that is plainly available and allow them to open up doors to increasingly complicated or unachievable issues that have been resolved through conventional approaches. This applies in particular to biological concepts specific to people. For particular, the particular class approach of human neural stem cells has already been studied with human brain organoids. Retinal organoids have also been used for testing changes between morphogenesis and timing of human and rodent tissue. In addition, GI tract organoids can also be employed to investigate the organized promotion of GI bodies, a method that shows crucial human change combined with animal laboratory. Organoids are also promising to model homosexuality for adults. The relevance of the crypt niche in stem-cell self-renovation and differentiation was previously studied by intestinal organoids. This applies primarily to organoids from adult progenitors such as the liver and stomach, which closely recreate regeneration processes seen in the adult organ. Although if numerous options of organoids are clear, it is important to remember their existing limitations. In the recapitulation of in vivo development, all organoid approaches that have been shown so far remain meticulously defined. For example, whereas retinal organoids finely show classical laminar composition, external parts do not shape; photoreceptors, for example, are short of being entirely developed to become light sensitive.

Consequently, brain organoids [34] recapitulate fast brain growth outcomes, but future features, for example, in cortical platelets, are not fully formed. The development issue appears to be a common impediment to organoid technologies and whether this will limit their research and therapeutic opportunities greatly is still to be explored. In the end, the lack of vascularization is usually an in vitro problem for organoids. Organoids have limited growth capacity, which may also impact their development because of nutrition supply restrictions. A whole subject of tissue engineering that has been tackled by the various techniques of vascularization. Spinners can provide healthier nutritional swaps with a size of up to a few millimeters in this example of organoids. Instead, endothelial cell co-culture can create systems like vascular systems. However, the transplantation of these tissues is possibly the most hopeful problem-solve, as was done with liver buds and kidney organoids that fosters hosts invasion [35, 36].

Organoids have significant potential as a way of drug testing and therapy for development and disease modeling. Potential initiatives will certainly get them closer to this prospect.
