**Preface**

This reprint presents extended versions of contributions to pHealth 2021, the 18th International Conference on Wearable Micro and Nano Technologies for Personalized Health, held on 8–10 November 2021 in Genoa, Italy, selected for the related Special Issue of the Journal of Personalized Medicine. The original papers have been published in the IOS Press Studies in Health Technology and Informatics 2021, volume 285.

The 2021 edition of pHealth emphasized the interrelated aspects of advanced pHealth, i.e., personalized, participative, preventive, predictive, and precision medicine (5P medicine) in health and social services. In that context, mobile technologies, micro–nano–bio smart systems, artificial intelligence and robotics, data management and analytics, machine learning and deep learning for personalized health, the Health Internet of Things (HIoT), systems medicine, public health, and virtual care are of interest. Those new technologies create new potential risks for security, privacy, and safety, resulting in new challenges for meeting the ethical and trustworthiness requirements of systems, partners, and processes. Bernd Blobel, as the long-term Chair of the pHealth conferences' Scientific Program Committee, as well as of the pHealth Steering Committee, has checked and edited every paper invited for publication in the MDPI JPM pHealth 2021 Special Issue before giving the green flag for formal submission. Mauro Giacomini, as Chair of the pHealth 2021 Local Organizing Committee, has managed the review process performed by at least two independent international experts.
