How to list only child categories?

Is there any way to list the child categories only? I just want to filter the Parent Categories

The following code is to display the subcategory instead of parent .
I am not sure this is the one as you are trying too.

 <ul> 
    <?php 
     $catsy = get_the_category();
     $myCat = $catsy->cat_ID;
        wp_list_categories('orderby=id&child_of=".$myCat); 
    ?>
    </ul>