We inhale oxygen, a vital gas for human survival. Oxygen is an essential element that our bodies require to produce energy through a process called cellular respiration. In this process, oxygen is utilized to convert glucose from food into adenosine triphosphate (ATP), which provides energy for various biological functions. The atmosphere contains about 21% oxygen, making it readily available for breathing. While oxygen is critical for life, it must be balanced with other gases in our environment, and the processes of photosynthesis by plants help replenish atmospheric oxygen levels.