The Packed Bubble visualization displays two numeric values simultaneously. Each bubble is defined by a dimension value, while the color and size of the bubbles are determined by the corresponding numeric measures. Sizes and colors of the bubbles make it easy to visualize outliers between measures and give a general sense of the distribution for the measures.
The example below shows Looker's System Activity components sized by query runtime in minutes and colored by query count. The ‘settings’ component has moderate relative query runtime in minutes but high query counts — indicating short but frequent visits.
This visualization requires one dimension and two measures.