A simple way to visualize flow is with **waterfall charts**. The waterfall chart is a good way to show the complexity that can sometimes be hidden in our cumulative numbers. Beware that this chart makes it harder to compare the specific sizes of growth or contraction between two subcategories.  The **Sankey chart**, while similar to an *Alluvial diagram* (see [Compare variables](Compare%20variables.md)) depicts *flow* of some kind, and the order of the nodes is stable. (Note that in the image just above, "Visualize a flow", the Sankey chart pictogram is wrong and confusingly shows the structure of an Alluvial diagram.) Sankey charts are used to visually represent the transfer of energy, money, materials, or the flow of any isolated system or process. Note that flows do not cross over each other.  The **Chord diagram** has been used to visualize the flow of migration. Over-cluttering becomes an issue with Chord diagrams when there are too many connections displayed.  A *Chord diagram* can also be used to interactively show the relationship among multiple entities of the same kind in a network (such as the words spoken to each other by the characters of the TV series "Friends").  A **Network graph** can show connections; Somtimes, the node sizes even represent another variable, and the connections can be weighted by the amount of flow. For example, this kind of graph can be used to visualize the social network from the TV series "Game of Thrones":