Originally Posted by Nick Theodorakis

Looking at the "biology" category (for which I am more familiar), it looks as if there is a mixture of disciplines that are categorized by subject matter (e.g., plant biology, or micobiology) or by technical expertise (e.g., molecular biology, or bioinformatics). A researcher might well consider herself a plant biologist because of her subject matter; she might also be regarded as a geneticist, a molecular biologist, or a biochemist (which is a biological discipline as mush as it is a chemistry one) depending on what kind of experiments she does on plants. Similar issues appear in the "chemistry" division; e.g., spectroscopy and chromatography are descriptions of techniques, and ones also commonly used by people describing themselves as biochemists.

Nick