Within seconds
Your body temperature drops about 1.6°F per hour until your reach room temperature.
Brain activity surges, then it stops.

Within minutes
Your cells begin dying due to lack of oxygen, and then starts to break down and leak beginning the process of putrefaction.
After hours
Eventually your muscles relax, causing you to release any remaining feces or urine.
Calcium builds up in muscles causing them to tense. This “rigor mortis” lasts roughly 36 hours.
Gravity pulls your blood down making skin look pale with reddish splotches.
Skin shrinks as it dries out making your hair and nails seem like they are growing.

After days
You start to smell terrible because your decaying body releases chemicals like putrescine / cadaverine.
You turn green in spots because enzymes in your organs start digesting itself usually with the help of bacteria.
Bugs eat you-maggots can digest 60% of a body within a week.
Hair starts to fall out.
You turn purple then black as bacteria continue to digest your body.

After Months
If your body is left at 50°F, it will take about four months for your soft tissues to decompose until just your skeleton is all that is left.

very informative post