Fetal development
| conception | zygote: | fertilized egg |
| 7-10 days | blastocyst: | inner group of cells, which will become the embryo, surrounded by an outer shell, which will become the placenta |
| 1-3 months | embryo: | highly differentiated |
| 11th week to birth | fetus: | Recognizably human. Heartbeat. Smiles, "walks," "breathes," reacts to pain. |