Software Defined Networking (SDN) and Network Function Virtualisation (NFV) have recently changed the way we operate networks. By decoupling control and data plane operations and virtualizing their components, they have opened up new frontiers toward reducing network ownership costs and improving usability and efficiency. Recently, their applicability has moved toward public telecommunications networks, with concepts such as the Cloud Central Office (cloud-CO) that have pioneered its use in access and metro networks: an idea that has quickly attracted the interest of network operators. By merging mobile, residential and enterprise services into a common framework, built around commoditized data centre types of architectures, future embodiments of this CO virtualization concept could achieve significant capital and operational cost savings, while providing customised network experience to high-capacity and low-latency future applications. This tutorial provides an overview of the various frameworks and architectures outlining current network disaggregation trends that are leading to the virtualization/cloudification of central offices. It also provides insight on the virtualization of the access-metro network, showcasing new software functionalities like the virtual Dynamic Bandwidth Allocation (DBA) mechanisms for Passive Optical Networks (PONs). In addition, we explore how it can bring together different network technologies to enable convergence of mobile and optical access networks and pave the way for the integration of disaggregated Reconfigurable Add Drop Multiplexer (ROADM) networks.