Small multiples split one crowded chart into many small ones, each showing one group.
The idea relies on repetition: once a reader understands one panel, they understand them all.
Every panel uses the same chart type, the same axes and the same colours.
The eye then compares shapes and levels across panels without reading any numbers.
Panels are arranged in a grid, often ordered by something meaningful such as size or region.
A highlighted line in each panel, with the other groups faint behind it, keeps the overall context.
Shared axes make small groups look small, which is honest, but can flatten their detail.
Where detail inside each group matters more than comparison, separate axes are an option if clearly labelled.
Too many panels shrink each one until labels and lines are unreadable.
Beyond a few dozen panels, each one becomes too small to read on a screen or a page.
Small multiples work with lines, bars, histograms, scatter plots and maps.
They are also called facets, trellis charts or panel charts.
Ordering panels by the value of interest, such as total sales, puts the most important groups first.
In practice they suit any question of the form: how does this pattern differ across groups?
The usual mistake is giving each panel its own scale without saying so, which makes every group look equally dramatic.