A body starts to decompose immediately after death, with visible changes such as greenish skin and bloating occurring within 18-48 hours. Under typical burial conditions in a coffin, decomposition begins within a year but can take up to 10 to 15 years to fully decompose to just skeletal remains. If a body is buried without a coffin, skeletonization typically occurs within five years. Complete breakdown of the skeleton can take about 20 years in fertile soil, but can last much longer in neutral or sandy soils. Environmental factors like temperature, burial method, and soil conditions significantly influence the rate of decomposition.