 Fagan (2013a, 2017) extends this cell lineage framework to cell-molecular and cell-organism relations, yielding a cell-centric multi-level model of development. Her view of the cell-molecular relation is that of systems biology: a cell state is a pattern of gene expression and molecular interactions that determines a cell’s structural and functional characteristics. The cell-organism relation is “enkaptic”—that is, cells reproduce and differentiate (the two defining stem cell abilities) and are collected or encapsulated into a higher-level system: gastrula, tissue, organ, or an experimentally-produced organoid or embryo-like structure. The higher-level system emerges via formation of a boundary separating it from its environment. So different levels or scales of a developmental process are related by “boundary-formation”. On this view, development is a process comprised of multi-layered interactive networks, arranged in strata (layers) related by an encapsulating boundary. Each network is related to the one below by boundary-formation, conceived as emerging out of (and imposing constraints on) smaller-scale interactions such that an encapsulating system is distinguished from its environment.