The Oxygenation Event, also known as the Great Oxidation Event, marks a pivotal moment in Earth's History when Atmospheric oxygen levels significantly increased due to Photosynthetic Activity by Ancient cyanobacteria. This event, occurring around 2.4 billion years ago, fundamentally altered Earth's environment, enabling the evolution of Aerobic life forms and leading to the Formation of the ozone layer that protects life from Harmful solar radiation.