 Whilst the genetic influence on development is fundamental, causation does not only occur from the bottom up, but also flows ‘downwards’ from more complex levels of organismal organization (e.g., tissue-specific regulation of gene expression).The result is that many features of organisms are emergent properties that are not encoded in the genome.Constructive development is manifest in context-dependent gene expression, physical properties of cells and tissues, exploratory behavior of physiological systems and learning.