**1. Introduction**

Owing to the fantastic potential of pluripotent stem cells (PSCs) to develop into all cell types in the body, regulating the differentiation of PSCs into particular tissue types is a substantial challenge. Early attempts to differentiate human PSCs (hPSCs) used twodimensional (2D) monolayer cultures, resulting in cells that showed germ layer markers but lacked tissue architecture [1, 2]. Because of the potential to generate differentiated cells for therapeutic applications, human-induced pluripotent stem cells (iPSCs) are being researched more and more in stem cell research [3, 4]. Recent research has concentrated on developing organoids from human iPSCs and avoiding the ethical problems connected with embryonic stem cell (ESC) usage. Initial attempts at three-dimensional (3D) structure generation relied heavily on aggregation and spontaneous differentiation, resulting in disorganized tissue mixes [4, 5]. Recently, incredible progress has been made in the *in vitro* development of 3D organized tissues—dubbed organoids. Organoid technology is a multidisciplinary technique that uses stem cells' ability to self-renew, differentiate into many lineages, and self-organize into organoids. Scientists have explored human PSCs and adult stem cells (ASCs) to create tiny tissue mimics that resemble a wide variety of organs [6]. Several research groups have now manipulated PSCs and ASCs *in vitro* to generate endodermal, mesodermal, and ectodermal cell-derived organoids. Organoid culture has been used to promote the development of various tissues, including the kidney, brain, lung, colon, stomach, breast, liver, etc. (**Figure 1**).

Organoid technology has the potential to produce organ-specific tissue organoids and can provide an unprecedented opportunity for effective modeling of human-specific disease and to simulate the physiology and complexity of tissue-specific ailments. Given the existing difference between animal models and human disease pathology, a paradigm shift was needed to model human diseases appropriately. The 3D human organoid platform can aid in acquiring a better knowledge of the pathobiology of human diseases [7]. Organoids throw light on human disease-associated signaling interactions, cell-cell communications, therapeutic target identification, therapeutic discovery, and screening, thereby decoding the process of disease development in humans. Organoids closely replicates human physiology and simulates disorders affecting many organ systems is a more viable alternative to *in vivo* animal models when studying regenerative medicine [8]. It has now become feasible to use a person's own stem cells for personalized disease models and precision treatment as a result of improvements in biobanking [9, 10]. This collection of chapters attempts to bring together professionals from a variety of fields in order to shed light on the use of organoids in human disease management.

**Figure 1.**

*Human organoids are vital in the progress of human biology research, preclinical investigations, and their translation into successful therapeutics.*

Organoid-based disease modeling is a rapidly evolving field with significant potential for integrating novel techniques into future investigations [6]. Recent breakthroughs in organoid technology, such as creating a unique organoid platform, the engineering of organoid complexity, and the incorporation of pathological characteristics, have accelerated the development of tiny tissue or organs on a dish. Novel technologies, such as high-resolution 3D imaging, organ on a chip, 3D printing, gene manipulation, and single-cell sequencing, have accelerated the development of organoids, which can provide unprecedented insight into the behavior of stem cells, as well as serve as a platform for preclinical research and theranostics [11, 12]. Genome editing, hybrid culture techniques, biobank development, and single-cell sequencing are all examples of cutting-edge technologies that may help generate more physiologically realistic human disease models, thereby altering the identification of new therapies. A combination of these approaches has the potential to push the frontiers of present scientific study, and future advances will almost certainly result in the development of new paradigms for battling human diseases [7, 12]. This book presents a comprehensive overview of organoids and has three sections: Organ-specific organoid, Patient-derived organoid and tumoroid, and Organoid commercialization.

## **2. Organ-specific organoid**

This section reviews how scientists are cultivating organ-specific tissue from stem cells, which has the potential to revolutionize the way diseases are investigated and treated. Retinal organoids (ROs) are unique to several exciting organoid types. ROs are 3D tissue constructs made from ESCs or iPSCs and accurately reproduce the spatiotemporal differentiation of the retina, making them useful

### *Introductory Chapter: Organoid Technology and Potential Applications DOI: http://dx.doi.org/10.5772/intechopen.104249*

*in vitro* models of retinal development and retinal disease [13]. ROs, available since 2011, allowed researchers to study retinal development (especially lightsensitive photoreceptors), pathology, and regeneration. The ROs' differentiation efficiency and development degree have improved dramatically during the last decade and offer many applications, including disease modeling. This section also reviews the role of ROs in evaluating disease pathogenesis, medication screening, and retinal regeneration treatment [14]. Although ROs have a promising future, their lack of structure and function, differentiation and culture constraints, and embryonic retina differences remain unsolved. Neural organoids, or cerebral organoids, are 3D *in vitro* culture systems produced from hPSCs that mimic the human brain's development. Specific distinctions between animal and human neurodevelopment have led to a dearth of information about human neurogenesis and understanding the pathological aspect. This section describes the applications of neural organoids in neurodevelopment and regenerative medicine. Advances in stem cell technology and the advent of the human-specific 3D neural organoid model are now widely used to study a specific aspect of the human brain and neurodevelopment. They can be vital in developing more effective therapeutics and regenerative medicine applications [15]. This section reviews current developments and future directions in the brain and retinal organoid developments and their applications.
