Ancillary services are essential for maintaining the stability and reliability of the power grid by regulating frequency, voltage, and power load. Key services include Reactive Power and Voltage Control, which stabilizes voltage levels, Contingency Reserves, which provide backup during outages, Black-Start Regulation for grid recovery after blackouts, and Frequency Regulation to balance supply and demand. Managed primarily by European TSOs, these services are increasingly supported by DERs like electric vehicles, battery storage, and solar systems. The future of ancillary services is shaped by technological advancements, market evolution, and regulatory adaptations to ensure grid resilience.