Explore the fundamental concepts of measurement and its significance in scientific endeavors in this 34-minute lecture from The Royal Institution. Delve into the International System of Units (SI) and learn about the upcoming changes to four key SI units, including mass and temperature. Discover how measurements are shifting from arbitrary standards to natural constants. Gain insights into various aspects of temperature measurement, from highly accurate thermometers to industrial sensors for harsh conditions. Examine the evolution of measurement systems, the importance of standardization, and the challenges in creating universal units. Understand the role of atomic clocks, the redefinition of the kilogram, and the impact of these changes on scientific progress. Conclude with a summary of how modern measurement techniques are revolutionizing our understanding of the world around us.