_Digital Twin, Blockchain, and Sensor Networks in the Healthy and Mobile City_ explores how digital twins and blockchain can be used in smart cities. Sections deal with promising applications for safe and healthy cities and current perspectives of blockchain and digital twins for future smart cities, helping us create happy, healthy, safe, and productive lives. The global smart cities market size was valued at USD 1,226.9 billion in 2022 and is expected to register a compound annual growth rate (CAGR) of 25.8% from 2023 to 2030. Digital twin refers to a simulation of physical products in virtual space. This simulation makes full use of physical models/wireless sensor networks/historical data of city operation to integrate big information (digital twin cities) under multi-discipline, multi-physical quantities, multi-scale, and multi-probability. * Describes the fundamentals of blockchain and digital twin * Explains how intelligent sensor networks can be used in healthy and mobile cities * Explores how blockchain and digital twin work with smart sensor networks * Discusses how future technologies can benefit the healthcare of everyday lives