The study of the growing complexity of the physical world is of great value to many scientific disciplines, including philosophy of nature, complexity theory, thermodynamics, and others. Here, I propose a systematic and quantitative method of describing the process of natural complexification throughout cosmic history, based on a list of the topical categories of PACS® 2008: Physics and Astronomy Classification Scheme 2008, published by the American Institute of Physics. I assume that each of the selected 349 level-3 categories corresponds to (...) a certain subset of natural phenomena, and I group them according to their first appearance in natural history. By analyzing their distribution, I derive certain qualitative and quantitative generalizations concerning the pace and scale of the growth of natural complexity. I contrast this approach with the results achieved by other methods and discuss its relevance to selected topics in philosophy of nature and philosophy of science. (shrink)