Choose one item on your outline to refine. You may want to choose the item that interests you most, the one you know the least about or the one that is least developed so far on your outline.
Research that topic to find the subtopics it includes. If you chose to refine chemistry, for example, you may find that it includes subtopics like biochemistry, inorganic chemistry organic chemistry and physical chemistry.
Insert the subtopics you found during your research into your outline under the topic you chose to expand, indent them at one level deeper with the appropriate tags (such as capital letters or Arabic numerals).
Repeat the process, starting with another outline item that you have not developed yet. You can choose an item from any detail level. For example, you could develop biology by finding the subtopics in the field of biology, or you could develop North American spider species by finding the names of specific spider species that live in North America. Continue choosing items to develop until your outline is detailed enough.