Have ever seen the microbes such as saprophytes on your food? These microbes are the primary decomposers of all dead organic matter. They are airborne or may be transferred to food by contact. Nothing kills appetite like finding a stinky colony of bacteria and fungi on your bite.
TEMPONAUT Timelapse has created a series of videos that explore these procesess. They have spent days (for example, 19 for strawberries) and months (2 for pineapple) recording these timelapses.