Stem cell therapy has emerged as a promising field in scientific research, offering potential treatments for various diseases. This review explores the discovery of different stem cells, their potential therapies, and the challenges they face. Stem cells are unspecialized cells capable of self-renewal and differentiation into various cell types. They can be categorized into totipotent, pluripotent, multipotent, oligopotent, and unipotent cells, each with varying differentiation potentials. Totipotent cells, like zygotes, can form all cell types, while pluripotent cells, such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), can differentiate into all germ layers. Multipotent cells, like hematopoietic stem cells, have a narrower differentiation range. The review discusses the derivation and culturing of stem cells, emphasizing the importance of quality control and teratoma formation assays. Methods such as enzymatic dissociation, manual passage, and the use of growth media are crucial for maintaining stem cell properties. iPSCs, generated from somatic cells, offer a promising alternative to ESCs, avoiding ethical concerns. The review highlights the significance of directed differentiation in regenerative medicine, where stem cells are guided to become specific cell types. Challenges include ensuring the safety and efficacy of stem cell therapies, as well as overcoming ethical and technical barriers. The turning point in stem cell therapy was marked by the discovery of iPSCs in 2006, which allowed for the reprogramming of adult cells into pluripotent states. This breakthrough opened new avenues for personalized medicine. The review also touches on the use of stem cells in pharmacological testing, tissue engineering, and the treatment of diseases such as Parkinson's and diabetes. Despite the potential, challenges remain, including the risk of tumorigenesis, the need for standardized protocols, and the ethical implications of stem cell research. Overall, stem cell therapy holds great promise for the future of medicine, offering hope for previously untreatable conditions.Stem cell therapy has emerged as a promising field in scientific research, offering potential treatments for various diseases. This review explores the discovery of different stem cells, their potential therapies, and the challenges they face. Stem cells are unspecialized cells capable of self-renewal and differentiation into various cell types. They can be categorized into totipotent, pluripotent, multipotent, oligopotent, and unipotent cells, each with varying differentiation potentials. Totipotent cells, like zygotes, can form all cell types, while pluripotent cells, such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), can differentiate into all germ layers. Multipotent cells, like hematopoietic stem cells, have a narrower differentiation range. The review discusses the derivation and culturing of stem cells, emphasizing the importance of quality control and teratoma formation assays. Methods such as enzymatic dissociation, manual passage, and the use of growth media are crucial for maintaining stem cell properties. iPSCs, generated from somatic cells, offer a promising alternative to ESCs, avoiding ethical concerns. The review highlights the significance of directed differentiation in regenerative medicine, where stem cells are guided to become specific cell types. Challenges include ensuring the safety and efficacy of stem cell therapies, as well as overcoming ethical and technical barriers. The turning point in stem cell therapy was marked by the discovery of iPSCs in 2006, which allowed for the reprogramming of adult cells into pluripotent states. This breakthrough opened new avenues for personalized medicine. The review also touches on the use of stem cells in pharmacological testing, tissue engineering, and the treatment of diseases such as Parkinson's and diabetes. Despite the potential, challenges remain, including the risk of tumorigenesis, the need for standardized protocols, and the ethical implications of stem cell research. Overall, stem cell therapy holds great promise for the future of medicine, offering hope for previously untreatable conditions.