2D cell cultures have traditionally been used as tumor models for drug development. Cancer cells cultured in a monolayer have a simple structure that shares minimal contact with their surrounding cells, while cell-specific functionality is degraded or lost during the culture process. For these reasons, it could be difficult to predict clinical outcomes using 2D cell culture assays. Therefore, the need for 3D cancer models is increasing, in order to perform accurate drug screening and verify the effectiveness of novel anti-cancer therapies.

Both spheroids and organoids are 3D structures composed of multiple cells.

Spheroids are clusters of broad-ranging cells derived from structures such as tumor tissues, embryoid bodies, liver, nervous tissue, or mammary glands. They don't require scaffolding and simply stick to each other, forming 3D clusters.

Organoids are complex clusters of organ-specific cells, such as those from the stomach, liver, breast, or bladder. They are made of stem or progenitor cells and self-assemble when provided with an extracellular scaffolding environment. Subsequently, they grow into microscopic versions of their parent organs and maintain their viability during 3D cell-based studies.