Often, already existing data can help answer your research question. Searching for such data is easier with well-maintained and annotated (= enriched with metadata) data. This applies for both data providers and subsequent users. Making research data available beyond a research project allows other researchers and research groups to retrieve the data when it has become relevant for research again.

If you want to reuse already existing data, you can use different search tools, including:

It is always important to check the copyrights and licences before reusing data and seek permission when necessary.