The papers in this special section provide the opportunity for researchers, practitioners, and application developers to review and discuss the state-of-the-art and trends of MCS (mobile crowd sensing)techniques and applications or propose new solutions. The ubiquitous sensor-rich mobile devices (e.g., smartphones, wearable devices, and smart vehicles) have been playing an increasing important role in the evolution of the Internet of Things (IoTs), which bridges the digital space and physical space at a societal scale. Their powerful computing/communication capacities, huge population, and inherent mobility make mobile-device networks a much more flexible and cost-effective IoT solution than static sensor networks.