Sankey Diagram is a data visualization type that depicts flows (of any kind) and their quantities in proportion to one another. It was named after Matthew Sankey, an Irish captain and engineer. In 1898, he drew a chart showing the energy efficiency of a steam engine, often referred to as the first-ever energy flow diagram.
Sankey Diagrams consist of nodes connected by lines or arrows. The width of the lines in this chart type depends on the amount of flow from source to target: the bigger the quantity, the wider the line.
Sankey Diagrams are popular in science, especially in physics. They are often utilized to visualize the transfer of energy (inputs along with useful and wasted output) and some other resources. A Sankey Diagram can also be helpful in showing diverse processes and their states.