Primary Sources are sources that you get directly from the person who created it. It should be original content and not use information from other sources. In many subject areas, you can use letters, diaries, news reports and songs/poetry as a primary source. They give you a direct view of what the person who experienced an event saw, heard, or felt.
When working in science and medical research, our primary sources are a little different. We want to find original research, where the authors actually did the tests, experiments, or observations themselves. The easiest way to find these types of resources is to filter your results by Publication Type, Methodology, and/or Document Type. Here's what to look for: