English: Schematic depiction of different approaches for organoid generation. Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are explored for research use. Somatic cells can be reprogrammed into iPSCs by introducing four transcription factors. As development proceeds, blastocysts differentiate into ESCs and further form all three germ layers: the endoderm, mesoderm, and ectoderm. The embryonic endoderm then generates the gastrointestinal system, heart, lungs, and liver. The mesoderm develops into the kidneys and blood vascular system, while the ectoderm forms the neural ectoderm, which eventually becomes the brain with its different regions, including the hippocampus, optic cup, cerebellum, and others. 3D organoid technology can recapitulate all the aforementioned structural and functional features in vitro