Miniaturized biological systems capable of mimicking complex organ architecture are transforming regenerative medicine. Organoids and lab-grown organs offer powerful platforms for modeling disease, studying development, and exploring therapeutic interventions without relying on animal models. Derived from stem cells and grown in three-dimensional culture systems, organoids self-organize into structures resembling the functional units of organs like the liver, intestine, brain, or kidneys. Coupled with bioreactors and advanced scaffolds, lab-grown organs are progressing toward clinical relevance, especially in transplantation and toxicity testing. Organoids and lab-grown organs bridge developmental biology with engineering, opening new frontiers for personalized treatment, functional organ replacement, and ethical drug discovery that mirrors in vivo responses with remarkable fidelity.