Table 1.

The key differences among cell cluster, spheroid and organoid

	Cell Cluster	Spheroid	Organoid
Complexity	Low (simple aggregation)	Medium (microenvironment mimic)	High (organ-specific architecture)
Cell Source	Any cell type	Tumor cells/stem cells/primary cells	Stem cells (pluripotent or adult)
Self-organization	Weak	Moderate	Strong (self-patterning & differentiation)
Functionality	No specific function	Partial pathological/physiological function	Near-native organ function
Culture Conditions	Conventional suspension culture	Low-adhesion substrate/serum-free medium	Growth factors + ECM (e.g., Matrigel)
Main Applications	Preliminary cell interaction studies	Tumor microenvironment, drug screening	Disease modeling, regenerative therapy