Aby Warburg and Nature

About two years ago I became interested in the German art historian, Aby Warburg, after having a conversation about him with a colleague.  I knew his name, but had only a superficial understanding of his methodology and research interests.  I understood that his dissertation presented the idea of iconography, but, my formal studies of the history of iconography had centered around Erwin Panofsky.  Panofsky, like so many other Jewish scholars, emigrated to America in the 1930s and he published the foundational, Studies in Iconology: Humanist Themes in the Art of the Renaissance, in English in 1939.  Somewhere along the way, I just never gave much thought to Warburg, something I now regret after having done a little research about him.