What causes things to rot or go bad?

Things rot or go bad primarily due to microbial activity, including bacteria and fungi, which break down organic matter. Factors such as moisture, temperature, and oxygen availability play significant roles in accelerating this decomposition process. Enzymatic reactions and chemical changes also contribute to spoilage, leading to the loss of freshness, flavor, and nutritional value. Additionally, exposure to light and air can exacerbate the deterioration of certain foods and materials.