Organoids are self-organizing in vitro three-dimensional (3D) tissue cultures containing multiple types of cells. Compared to traditional two-dimensional (2D) cell culture systems, 3D organoids better replicate the architecture, complexity, and physiology of an organ (Figure 1). In addition, 3D organoids are easier to scale up and more cost-efficient when compared to animal models. In the past decade, organoid technology has risen rapidly and become increasingly more prevalent among researchers. They can be cultured long-term and are easily amenable to genetic, molecular, and cellular analyses. Organoids can be derived from embryonic stem cells, induced pluripotent stem cells, adult stem cells, and tumor cells or primary tissues. Currently, 3D organoids have been created for multiple organs, including the brain, lung, stomach, small intestine, colon, pancreas, kidney, liver, prostate, etc.