Microbes include bacteria, parasites, viruses, and fungi that constantly evolve. Antimicrobial resistance (AMR) happens when microbes change, becoming harder to treat in individual human and nonhuman animals and plants with antibiotic, antiparasitic, antiviral, and antifungal agents. Resistant pathogens are easily transmissible across human and nonhuman ecology, and this theme issue attends to ethical, clinical, and policy dimensions of this set of problems. National and international burden of AMR has been assessed in terms of infection incidence, deaths, hospital length of stay, and location-specific costs of developing and applying specific pathogen-drug combinations to try to save lives and preserve food supplies. Routine and focused surveillance is key to understanding microbiological, individual, social, and ecological root causes, downstream effects, and sources of domestic and global inequity in AMR.