The human brain increases its total volume by folding its surface area into peaks and troughs called gyres and sulci. The process whereby this happens is called gyrification (not sulcification, for some reason). The total surface area of the brain is about one or two pages of newspaper, much larger than the surface area of the skull.
The intestines curve back and forth within the abdomen and increase their total length to about 22 feet. This is not exactly inward folding, but the inside of the intestine has villi and microvilli that do look like an inward folding, increasing the surface area by several orders of magnitude, until it is about the total area of a tennis court!
I am looking for a word generally appropriate to this geometry, but applicable in a non-biological context. It should carry connotations of increasing complexity induced by inward folding. Gyrified is bad because nobody knows what it means, it only talks about brains, and could have been sulcified. I have been using involuted, but it’s not quite right because it involves rolling or curling in a spiral manner, coming from the architectural term volute, which is a spiral ornament on an Ionic column.