RowMinHeight is an option for GridBox which specifies the minimum total height in units of font size that should be allowed for each row.
The default setting RowMinHeight->1 forces each row to have a total height which at least accommodates all the characters in the current font.
RowMinHeight->0 reduces the total height of each entry as much as possible, allowing entries containing characters such as x and X to be different heights.
See Section 2.9.11.
See also: RowSpacings, RowAlignments, RowsEqual, ButtonMinHeight.
New in Version 3.