# Area Chart
An area chart shows changes in quantities over time. It's similar to a line chart, with the area under the line filled in with color.
It's best used with multiple lines (**series**), and a continuous primary axis. Generally, the X-axis is the primary axis.
The primary axis can be Quantitative, Temporal, Ordinal, or Nominal. It has an automatic setting, but this can be manually set as well.
### Secondary Timeline
**`TIP`**: A temporal axis works well to show changes over time, and can be used as a secondary timeline on your dashboard. If the data contains a column that aggregates to a larger unit of time (e.g. week number of study), this can be plotted as an aggregated timeline using that column (week number) as the axis. This is a way to simulate the unit changes that are available in the actual timeline panel.
Using an area chart as a secondary timeline, using a temporal axis
Using an area chart as an aggregated secondary timeline, using a week number instead of temporal axis
### Interpolation
When choosing your chart type, the default is linear interpolation, but [other options](/instructions/adding-and-editing-panels/charts-panel.md#interpolation) may be more appropriate for your data.
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