Only a field like medical and scientific illustration could utilize a combination of: tiny brushes with the bristles cut down to nubs; little files to wear away at pastels and charcoals; sandpaper to make your pencils microscopically sharp; medical grade scalpels for the finest scraping available. I have to admit, I love detail. There hasn't been much call for a commercial application of my ability, since I avoided the medical school requisite, but if you're looking for realism down to the pores, give me a try!