The sulfur cycle is the natural process by which sulfur moves through the environment, including the atmosphere, soil, and living organisms. Sulfur exists in various forms, such as sulfate in water and hydrogen sulfide in the atmosphere. Microorganisms play a crucial role in converting these forms, allowing sulfur to be absorbed by plants and eventually passed through the food chain. When organisms die or produce waste, sulfur returns to the soil and atmosphere. It can then be reabsorbed by plants or transformed back into gases, completing the cycle. Human activities, like burning fossil fuels, can disrupt this cycle, leading to environmental issues such as acid rain.