Cell therapy (also known as cellular therapy, cell transplantation, or cytotherapy) is a treatment in which living cells are injected, grafted, or implanted into a patient to achieve a therapeutic effect, such as by transplanting T-cells capable of fighting cancer cells via cell-mediated immunity during immunotherapy or grafting stem cells to regenerate diseased tissues. Scientists experimented with injecting animal material in an attempt to prevent and cure diseases in the eighteenth century, and cell therapy was born. The transfer of autologous or allogeneic cellular material into a patient for medicinal purposes is known as cell therapy. Cell therapy is still evolving today, with continuing clinical trials for safety and efficacy, and a global market predicted to grow from USD 9.5 billion in 2021 to USD 23.0 billion in 2028. Cell therapy incorporates unicellular and multicellular therapies based on stem cells and non-stem cells. It usually uses autologous or allogeneic cells, and it may involve genetic engineering or formulation changes. It can be used topically or as injectables, infusions, bio scaffolds, or scaffold-free systems. Cell therapy is used in a variety of therapeutic fields, including regenerative medicine, immunotherapy, and cancer treatment.