The patent literature includes millions of publications. The current prior art in all technical fields can be found in these publications. In order to check whether an invention or a research development is not already known, it can be useful to carry out a timely search in the patent literature. It is moreover possible to keep an eye on the activities of competitors in the patent field by carrying out regular searches. Patent literature can also make a useful inspirational contribution during a development process. Access to a large part of the patent literature can be obtained via the free Espacenet database at nl.espacenet.com. It is however necessary to take into account here that patent applications are usually only published after 18 months. It may therefore be the case that someone else has already applied for patent on an invention, but that the invention does not yet appear in the database.