Centroid/Center of mass

Hi,

I have a COMSOL geometry composed of many different domains, each acting as an individual "grain" structure in a metal. I would like to find the centroid of each individual domain. I could find the centroid of the whole geometry numerically using MATLAB commands, but I need to find the centroid of each domain. Actually, as long as I can somehow retrieve the coordinates of ANY point in each domain, it would suffice. Is there a way to do this?