Scientific and other facts are excluded from copyright protection . As such, for scientific facts, we do not generally need to worry about whether Fair Use applies. While facts are not copyrighted, they are often buried within copyrighted documents such as published journal articles. Content within journal articles that are not clearly facts may then be copyrighted and/or open to debate about reuse of this content via Fair Use.
Some examples of facts in scientific journal articles are the melting point of gold, the chemical structure of Vincristine, or the bond dissociation energy of a carbon-hydrogen bond. Reuse of these facts does not require any permission, even if they were originally published in a copyrighted document. You can reuse this type of data in your own work. You will, however, want to give proper attribution and cite the original resource, so that other researchers know the origin of the data. Some exceptions exist as it is often acceptable to not cite well-known facts (e.g. at sea-level, water boils at 100 °C).
In contrast, any descriptions, explanations, figures, and illustrations are generally protected by copyright in journal articles. To reuse this material, you will need to ask permission from the copyright holder or determine if Fair Use applies [1, 2].
A few years ago, I asked two scientists, who are experts in data reuse, if scientific photographic images count as facts. So for example, a microscope image of a cell, or a nanometer length scale image of a material’s microstructure. One scientist replied “no, these images are not facts because they are a photograph, and photographs can be copyrighted.” The other scientist replied “it depends on how good your lawyer is!”
Happy Fair Use Week!
 Copyright Basics from the US Copyright Office, http://www.copyright.gov/circs/circ01.pdf
 Code of Best Practices in Fair Use, http://www.arl.org/focus-areas/copyright-ip/fair-use/code-of-best-practices#.VsNUgvkrLmE