Fig. 2 |. Organoid cell sources and types.

a | The initial cells used for organoid culture can be human adult stem cells, pluripotent stem cells or primary tissues collected via biopsy. Each cell type has associated advantages and disadvantages as a source for organoids. b | Although each type of organoid develops with unique morphological and physiological features, a general pattern of development is followed. Different studies may desire organoids in different stages of development or fabrication platforms. The proliferation and early differentiation of single cells and cell clusters leads to the generation of early-stage organoids, sometimes referred to as spheroids. Late-stage organoids are structures that resemble native tissue morphology, contain correctly oriented and specialized cells, and display organ-like processes. Organoid cultures are often placed within a 3D matrix at the single-cell or spheroid phase. The physiological relevance and complexity of organoids can be improved by various biofabrication techniques.