In Antarctica, scientists drill deep into the ice to extract long cylinders known as ice cores. These cores act like time capsules, preserving air bubbles that were trapped when snow fell and compacted over thousands of years. The air inside these bubbles contains the exact composition of Earth's atmosphere from the time it was trapped, making them invaluable for studying past climates. While the ice itself is not the main focus, the trapped gases, dust, and chemical traces within each layer provide critical information about ancient environmental conditions. By analyzing the composition of these air bubbles, researchers can determine historical levels of greenhouse gases like carbon dioxide and methane, as well as past temperatures. The ratios of oxygen and hydrogen isotopes in the air bubbles help scientists estimate the temperature at the time the snow fell. Layers with higher concentrations of heavier isotopes indicate warmer periods, while lighter isotopes suggest colder conditions. This technique effectively turns each centimeter of ice core into a thermometer that measures past temperatures, allowing scientists to reconstruct climate changes over tens of thousands of years. The European project Beyond EPICA is focused on studying these ice cores to gather data on Earth's atmospheric history. Recently, an international drilling effort achieved a record-breaking continuous ice core that spans multiple glacial cycles. Volcanic eruptions have left distinctive layers of ash in the ice, which serve as markers for synchronizing data from different drilling sites. These ash deposits, identifiable across thousands of kilometers, help scientists align timelines and ensure the accuracy of their climate reconstructions. Near the surface of the ice, scientists can find traces of human activity, such as radioactive fallout from nuclear weapon tests conducted in the 1950s and 1960s. These tests created a clear chemical signature in the ice, which acts as a chronological marker similar to volcanic ash. The peak of nuclear testing in the early 1960s and the Chernobyl disaster in 1986 provide two key reference points for dating the most recent layers of ice. This allows scientists to precisely date recent climate changes without needing to count every layer individually. The ice cores also contain a variety of impurities, such as industrial lead, Saharan dust, and soot from distant fires, each telling a story about different periods in Earth's atmospheric history. These impurities can be natural, like dust from ancient deserts, or human-made, like pollutants from industrial activity. The real scientific work begins in the laboratory, where researchers carefully release the trapped air bubbles and analyze their composition under vacuum to prevent contamination. This meticulous process allows scientists to study the Earth's past climate with remarkable precision.