A few minutes after death, the corpse begins to decompose. Numerous organisms, such as insects, bacteria, fungi, and animals, use the carrion as a nutrient source. The activities of these organisms, especially insects and microbes, are the major forces of decomposition. Specifically, the decomposition-associated microbial community (microbiome) plays an important ecological role, as decomposition is critical to nutrient cycling and energy flow. Furthermore, the process of decomposition is affected by many environmental factors including temperature, humidity, light, oxygen, and soil pH. Forensic entomology is studied widely and used to estimate postmortem interval (PMI) or time since death, but with known limitations. As a result, researchers are exploring more accurate methods by studying the microbial communities of mammal cadavers, human corpses, and surrounding gravesoils. These investigations have documented temporal successions in the microbial communities' composition and structure with potential to be used as a “microbial clock” to estimate PMI.