The essential behavior of a treemap is to split the space into boxes, where the area of each box corresponds to the value being visualized. When values differ by orders, it is natural to get tiny boxes next to larger ones. You can check this example
for a possible way to extend the visualization with tooltips, so that you can display more details even for smaller items.
As for the ScrollViewer - RadTreeMap does not specify its own size, but it uses the size provided by its parent. When placed in a grid, RadTreeMap will be stretched to take the entire grid cell. When placed in a control, that measures its children to infinity, RadTreeMap will not be rendered. The ScrollViewer control measures its child to infinity in both directions, hence the behavior you have observed. In this case you need to provide explicit dimensions and you will be able to see the control.
the Telerik team
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