Hi Sunil ,
With treemaps, Size and Color are the crucial elements. You can place measures on Size and Color, but placing a measure anywhere else has no effect. Treemaps can accommodate any number of dimensions, including one or even two on Color. But beyond that, adding dimensions only breaks the map into an ever greater number of smaller rectangles. For information on how to place two dimensions on Color in a treemap.
Size mark card is fixed with Tree Maps. you cannot change the size onto Tree Maps
While working with tree map both the size of the rectangles and their color are determined by the value of Measure you use in the tree—the greater the sum of Measure for each Dimension, the darker and larger its box.
and same applies with ctrl+B shortcut also.