As a relatively new interdisciplinary endeavor, workers in this field attempt to understand organismal interactions, both intra- and interspecific, mediated by chemical substances such as hormones, pheromones, kairomones and phytoalexins. These interactions occur at all taxonomic levels: between uni- and multicellular organisms, microbes and plants, plants and plants, plants and animals, microbes and animals and various species of animals. Study of such interactions has accelerated in recent years through joint efforts of biologists and chemists in basic and applied research in the laboratory and field. The master of professional studies degree requires graduate coursework credits and graduate seminars. Depending on the area of study, students may complete the M.P.S. degree with coursework and seminars, or a combination of coursework, seminars, and professional experience (internship). Professional Experience Option option requires at least 30 credits of graduate coursework, of which 24 must be taken in residence at ESF.