Interconnecting cyber-physical systems in networks leads to the creation of cyber-physical system-of-systems. In a cyber-physical system-of-systems (CPSoS), systems communicate by exchanging and sharing data and information, which this chapter also refers to as interoperability of information. To ensure reliable and secure interoperability of information between distributed cyber-physical systems, using blockchain technology or distributed ledging technology for distributed entities is an interesting option. Such a blockchain must, at a minimum, be fault tolerant and enable the entities involved to reach consensus on the information transactions that are to be performed. Once consensus about transactions between cyber-physicals is reached, it must be possible for these to record consistently the used data in a distributed ledger that provides a permanent shared overview of completed information transactions. The development of the new technology we call blockchain creates a new and as yet unfathomable reality of interconnected autonomous and self-organising cyber-physical systems that have the ability to make decisions about or for us as human beings.