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Only 12 hours after an egg cell is fertilized by a sperm cell, the egg cell starts to divide. As it continues to divide, it moves along the fallopian tube toward the uterus at about 1 inch per day.
Although the Roman numeral for the number 4 has always been taught to have been "IV," according to historians, the ancient Romans probably used "IIII" most of the time. This is partially backed up by the fact that early grandfather clocks displayed IIII for the number 4 instead of IV. Early clockmakers apparently thought that the IIII balanced out the VIII (used for the number 8) on the clock face and that it just looked better.
Although puberty usually occurs in the early teenage years, the world's youngest parents were two Chinese children who had their first baby when they were 8 and 9 years of age.
Throughout history, plants containing cardiac steroids have been used as heart drugs and as poisons (e.g., in arrows used in combat), emetics, and diuretics.
Vaccines prevent between 2.5 and 4 million deaths every year.