Energy is an important crosscutting concept in all science disciplines, and energy conservation is widely regarded as one of the most important principles in physics. Over the years, numerous graphical representations have been proposed that allow learners of physics to visualize energy states and dynamics in a particular situation. Each diagram highlights different aspects of energy and therefore may represent different conceptualizations of energy. Bar charts, or example, foreground the idea of multiple "categories" of energy to account for the distribution of energy in a system across those energy types. Similarly, pie charts highlight "relative distribution" of energy among different energy types. While bar charts are able to represent negative energy, pie charts emphasize that there is a certain, total amount of energy available that is distributed over different types. Various energy tracking diagrams (e.g., PET energy source-receiver diagrams, Energy Tracking Diagrams) foreground the "localization" of energy along a chain of energy transfer processes and within the involved objects.