Hierarchical clustering analyses (HCA) of binary signals. Dendrograms obtained by means of a HCA of the binary signals and log-log plots of the number of clusters as a function of the inter-cluster interval length obtained from controls (A) and GliA electroporated (B) and Shh non-ventralized (C) and Shh partially ventralized (D) electroporated midbrains. The dendrogram reveals that mNEcs are organized as clusters of different hierarchies (clusters within clusters). The height of the connectors (Π) indicates the level of aggregation, i.e., the scales at which two clusters of a given hierarchy aggregates into a single cluster of a higher hierarchy. The log-log plots show a power law behavior revealing the absence of a typical mean cluster size and that mNEcs are distributed in a continuous hierarchical set of clusters within clusters across scales.