 Waddington’s own later theorizing took a mathematical turn, interpreting the notion of a field in terms of spatial relations and using Réné Thom’s topology to theorize developmental pathways as an epigenetic system (1968). This work emphasized the concept of “chreod”, a trajectory (directed path) of normal development within multidimensional space, with axes for time, three spatial dimensions, and concentrations of chemicals. Although not fruitful in biology at the time, Waddington’s mathematical approach anticipated twenty-first-century alternatives to the idea of genetic control (see  Section 10).  In that context, the landscape model has experienced a renaissance. The underside image is replaced by complex gene regulatory networks, topside surfaces explicated in terms of systems biology and/or stem cell concepts (Fagan 2012, 2013a). Fusco and colleagues (2014) discuss recent theoretical proposals (e.g., Wang, Wang, &amp; Huang 2010) to “rehabilitate” Waddington’s landscape as a dynamical systems model, which require significant changes from the original. They conclude that landscape models (updated or not) are good for visualizing cell differentiation but not other important developmental processes—and so not well-suited for a comprehensive theory of development. As a metaphorical aid to understanding, however, Waddington’s landscape remains influential. Jan Baedke (2013) examines its broader impact across the life sciences, extending beyond organismal development to developmental psychology and cultural anthropology.