  We propose a physical model for developmental process at cellular level to
discuss the mechanism of epigenetic landscape. In our simplified model, a
minimal model, the network of the interaction among cells generates the
landscape epigenetically and the differentiation in developmental process is
understood as a self-organization. The effect of the regulation by gene
expression which is a key ingredient in development is renormalized into the
interaction and the environment. At earlier stage of the development the energy
landscape of the model is rugged with small amplitude. The state of cells in
such a landscape is susceptible to fluctuations and not uniquely determined.
These cells are regarded as stem cells. At later stage of the development the
landscape has a funnel-like structure corresponding to the canalization in
differentiation. The rewinding or stability of the differentiation is also
demonstrated by substituting test cells into the time sequence of the model
development.
