Two microscopic cells come together. Within three weeks, those cells have formed a foetal mass with a heart beat. By two months parts are starting to distinguish themselves, limb buds, head, face, eyes, etc. By the fourth month the fetus is visably human including visibly distinct gender, albeit the proportions are still working out and organs are developing. Fetal urine is the amniotic fluid that is inhaled to develop the lungs and swallowed. By the start of the third trimester, the fetus is developed enough it is possible although difficult to survive. By the seventh month the survival rate has vastly improved, and at the eighth month, the baby is basically developed and survivable, but hangs on another month for good measure. Amazing stuff!
My wife recently had a baby. Until she was pregnant I never appreciated how amazing it all is. When she delivered, I was just blown away by how strong she was for starters, but what we/her had just created. Every day I see my son do something new and amazing and he is only 7 months old. It really is mind boggling, and I think for many you don't realize it until you experience it.