*metaNodePlugin2* is a Cytoscape plugin that implements a collapse/expand abstraction for hierarchical groups of nodes. When used with the *namedSelection* plugin, these groups are shown in the Groups tab in the Cytoscape Control Panel. *metaNodePlugin2* can aggregate the attributes of the members of a group into a single node that represents the group (the meta node). There are a variety of aggregation mechanisms depending on the attribute type, from concatenation for Strings and Lists to average and sum for Integer and Double attributes. A collapsed meta node can be visualized in three different ways: as a nodeChart, as an embedded network, as a normal node. An expanded meta node can be visualized in two different ways: either hidden or as a node with member edges to each of its children. Meta nodes may also have independent attributes and edges in addition to aggregated attributes and edges that reflect their children. Once the plugin is installed, there will be a new MetaNode Operations menu under the Plugins menu. There will also be a new Metanode operations node context menu.
