WEBVTT 00:00.000 --> 00:02.600 Approximately 24 to 30 hours after fertilization, 00:02.633 --> 00:05.733 the zygote completes its first cell division. 00:05.767 --> 00:07.600 Through the process of mitosis, 00:07.633 --> 00:14.367 one cell splits into two, two into four, and so on.