Fabian Theis characterized a cell as an input-output system with memory and multiple levels of molecular specifications, extending beyond RNA.

“And that's sort of, I think, a quite deep question. If you really think about it, that's maybe even a bit of a holy grail in computational biology, systems biology, sort of this, this input output system that is a cell with memory and like with all its specifications and with all the different sort of levels of molecules and so on, not just RNA.”