Changing size of thumbnails
 

Hi All
You know when a user clicks on a category and a whole listing of products are shown on the page. The size of those thumbnails are too small. How can I change that default size?
Because personally I think they're too small. Is there somewhere i can change that in some code?

Thank you!

Admin Area - General Settings/Appearance options

Thumbnail width in the products list:

thx!