The concept of network flow is now a critical part of todays IT infrastructure. Integrated into most networking equipment, including routers, switches, access control devices, encryptors, performance enhancement products, wireless access points, cable modems, servers and end systems, network flow technology has made a massive impact in the networking industry. Given that the next generation of network equipment are OpenFlow enabled SDN switches, with the ability to define and control network function at the individual flow level, it seems that network flow technology still has a long way to go. The advances in network flow technology have only been possible because of advances in network flow monitoring. In this presentation, we'll discuss the history of network flows and network flow monitoring, the nature of current network flow monitoring technology and how network flow data has become a necessity for ISPs, IT enterprises, and government networks in managing network operations, performance and security. And we'll close with a discussion of the importance of network flow monitoring for new network strategies, such as software defined networks (SDN).