Organoids are ultra-small, self-assembled three-dimensional tissue cultures derived from stem cells. They can be created from both pluripotent stem cells (PSCs) and adult stem cells (ASCs) by simulating the biochemical and physical characteristics of tissue development and homeostasis.

Stem cells exhibit an intrinsic ability to assemble into complex structures. When placed within a hydrogel (often Matrigel) and in the presence of suitable exogenous factors, stem cells can be coaxed into forming structures containing organised clusters of cells.

Organoids serve as a better in vitro model compared to 2D or 3D co-culture systems. Applications for organoid research include organ development, disease modeling, drug penetration in the centre of the tumor mass, drug screening, and toxicity testing.

Organoids reiterate biological parameters including spatial organisation of heterogeneous tissue-specific cells, cell-matrix interactions, cell-cell interactions, and certain physiological functions. They bridge a gap in existing model systems by providing a stable system for mimicking in vivo physiology.

For spheroid formation, methods include suspension culture, non-adherent surface methods, hanging drop methods, and microfluidic methods.