Biosignature gases are gases emitted by living organisms that can be used as indicators of their presence. These gases can include methane, oxygen, carbon dioxide, and other volatile organic compounds. Scientists use biosignature gases to detect and study microbial life in extreme environments on Earth and potentially on other planets. By analyzing the composition of these gases, researchers can gain insight into the types of organisms present and their metabolism. This research area is important for understanding the potential for life beyond Earth and for astrobiology studies.