Copyright for scientists TL;DR: Copyright protects creative forms of expressions, not the content. In particular, facts or ideas cannot be copyrighted. On the side, we note that therefore mathematical proofs are not copyrightable. Even if something is copyrighted, it is usually possible to use quotations (including images) from such works in your own scientific publications. If in doubt, it is best to get permission from the copyright holder. Otherwise, one needs to check national copyright law - usually quotations are allowed in one’s own creative works, but only if this is necessary for the discussion and the copied amount is not larger than necessary.