IoTeX aims to become the privacy-centric and scalable spinal cord and nervous system for IoT.  IoTeX is a network of many blockchains that are hierarchically arranged, where many blockchains can run concurrently with one another while retaining interoperability. In the IoTeX world,  the root blockchain manages many independent blockchains, or subchains. A subchain connects to and interacts with IoT devices that share something in common, e.g., they have a similar functional purpose, operate in similar environments, or share the similar level of trust. If a subchain does not function well, e.g., being attacked or experiencing software bugs, the rootchain is completely unaffected. In addition, cross blockchain transactions are supported to transfer value and data from subchains to the rootchain or from one subchain to another via the rootchain.