This is mainly concerned with nature as they studied the physical world hence they are also called physicalists and cosmologists. This is a very old field of thought that was uniquely Greek. It’s amply explained by the Wikipedia article and I can’t really add anything to it since it’s so well established already. I sometimes include things just to make you aware of them and for completeness. As far as I know there is no input from anyone outside of Athens since it was so long ago.