Each registered participant who submitted successfully an abstract to HYPERFINE2021 are warmly invited to submit full paper to appear in the Conference Proceedings. As for the previous HYPERFINE conferences, the Conference Proceedings will be published in the journal Hyperfine Interactions (published by Springer Nature). Invited talks as well as oral and poster presentations are considered to be included in the Conference Proceedings, upon appropriate peer reviewing. All manuscripts will be peer reviewed according to standard international procedures before being accepted for publication.Further details will follow in due time.