**ITS-90** (International Temperature Scale of 1990) is the internationally recognized standard for defining and calibrating temperature measurements. Established to ensure global consistency and accuracy, it serves as a practical reference for thermometry across scientific, industrial, and metrological applications. Key features include:  

1. **Fixed Points**: Defines specific reproducible temperature points using phase transitions of pure substances (e.g., triple point of water at **0.01°C**, freezing points of metals like aluminum, silver, and gold).  

2. **Temperature Ranges**: Covers **0.65 K** (−272.5°C) to **1357.77 K** (1084.62°C), divided into sub-ranges with prescribed measurement instruments (e.g., platinum resistance thermometers, gas thermometers, or radiation pyrometers).  

3. **Standardization**: Replaces older scales (e.g., ITS-68) to reduce discrepancies and align with thermodynamic principles (Kelvin/Celsius scales).  

4. **Applications**: Critical for laboratories, manufacturing, meteorology, and research to ensure traceable and comparable temperature data.  

ITS-90 is maintained by the **International Committee for Weights and Measures (CIPM)** and underpins modern temperature-sensitive technologies and scientific advancements.