Discover how 3D intestinal organoids—mini-gut tissues grown from stem cells—are transforming preclinical drug testing. We break down how these models capture human barrier function, absorption, metabolism, and host–microbiome interactions better than animal systems, enabling smarter toxicity profiling and efficacy screening. From patient-derived organoids for precision medicine to organoid-on-chip platforms, we cover practical workflows, readouts (TEER, imaging, omics), and what it takes to translate in-vitro hits into clinical candidates.