Now you’ve gone and done it and fertilized an egg, you dirty birds. Nice work.
The fertilized egg is now a zygote. Which I originally thought was the creature Gandalf fought in the Lord of the Rings, but that was a Balrog. My bad.
It travels down the fallopian tube for a few days and divides to form a ball of wee cells that are even smaller than the period at the end of this sentence.
The zygote continues to divide, creating an inner group of cells with an outer shell (I like to envision an M&M but I doubt that’s the case) becoming a blastocyst. The blastocyst implants itself on your uterine wall around day six.