How to use supersom Grid-X and Grid-Y to better cluster the matrix?

[Linhua-Sun]

Hi：
I am wondering how to use supersom? Two parameters (Grid-X and Grid-Y) can be adjusted? What does it mean?

For example, the above figure show the result from hclust. But I am more interesting in those regions with more on the center area, while less values in left and right area. Can I use supersom to better cluster the matrix?
Thanks.