**6. 2D vs. 3D cell cultures: morphology and other characteristics**

Cell cultures that are 2D and 3D clearly differ with respect to their cell morphology as well as other characteristics. Cell cultures that grow in controlled flat environments, such as a Petri dish, are 2D cell cultures [6], and as such have cells that are flat in morphology [7]. Cell cultures that are 3D involve cells that are combined and shaped into a 3D spheroids using surrounding milieu or specialized conditions [7]. Cell viability also differs between 2D and 3D cell cultures. For example, 2D breast cancer cell cultures showed greater cell viability than 3D breast cancer cells [79]. Drug efficacy may also differ in 2D and 3D cell cultures [79].
