The energy industry is changing. In response to the need to decarbonise our energy usage, new decentralised forms of electricity generation have evolved, supported by smart grid technologies. These technologies are also changing the way we use electricity, leading both residential and business users to become increasingly active in their energy usage. The challenges of decarbonisation, decentralisation and digitisation have the potential to create whole system opportunities by transforming the way distribution networks behave and creating new flexibility market opportunities for potential service providers. These markets will enable Flexibility Services to compete alongside traditional investment options for all relevant network reinforcements or upgrades of significant value, and to make the most cost-effective investment decisions in the future. This chapter describes the need for Distribution System Operation to harness these changes and ensure the efficient and secure transition of the local energy systems to meet net zero.