A baby’s first poop is made of meconium, a sludgy substance in the intestines made up of in utero waste. Meconium is really a mixed bag, containing hair, dead skin cells, bile, water and amniotic fluid. This all comes out within the first 24-48 hours after birth. It’s greenish-black in color, but as nasty as it sounds, it supposedly doesn’t have a strong smell.
Learn more about meconium here. Also check out some more weird and gross facts here.