A scholar who is fascinated with a subject and knows a lot about it might write a monograph, or a long, detailed paper on one topic.
If your favorite subject in school is the study of insects, you may one day write a monograph on entomology, full of details about beetles and wasps. A monograph is usually researched carefully, with plenty of footnotes along the way. The thesis or dissertation a college student writes as a requirement for getting a degree is one type of monograph. The word comes from the Greek mono, "single," and graph, "something written."