"The notion of a ‘‘cell type’’ has arisen as a matter of convenience in cataloging, and of historically limited techniques for measurements. [...] With new technologies to measure both the fixed and dynamic ‘‘states’’ of single cells today, it is unclear whether or not this modest classification remains appropriate. Rather, an opportunity now presents itself to redefine the meaning of cell type to encompass the dynamic landscapes on which cells reside"

"A useful way to classify cells might thus be a multiscale and multi-parameter cell-type space [...] This could result in a cell type classification system with some subpopulations of cells continuing to cluster into clearly separable groups while other cells might lie on a continuum due to small differences but distinct behaviors. [...] Clearly the definition of a cell type needs to be addressed with additional data that integrates cell organization with cell function and gene expression programs."

"Functioning cells are not static, as coordinated interactions of multiple cellular constituents give rise to function. Therefore, the best descriptor of cell type may be a dynamical measure of the rates of the cellular constituent changes giving rise to particular physiologies."