April 14 marks World Quantum Day, celebrating advancements in quantum physics and the significance of the Planck constant, valued at 6.626 x 10^-34 J s. This constant is essential for describing energy behavior at the smallest scales and is foundational to quantum mechanics, which underpins technologies such as GPS navigation, MRI scanners, and smartphones. The choice of April 14 is not random; it corresponds to the first digits of the Planck constant (4.14). The impact of the Planck constant extends beyond theoretical physics, as it played a pivotal role in redefining the kilogram in 2019. Previously defined by a physical artifact, the kilogram is now based on precise measurements of the Planck constant, allowing for a universal definition that does not rely on a physical reference. This change reflects the importance of constants of nature in standard measurements.