Walking on the street, a pair of twins dressed in the same clothes can always attract the envious eyes of pedestrians. Some twins are almost the same in appearance and sex. This kind of twins, often [monozygotic twins], is two babies developed from the same fertilized egg. However, the twins of a man and a woman, or twins that do not look very similar, may be [double-egg twins], that is, two babies developed from the fertilization of two eggs respectively. Double-egg twins account for about 2/3 of the total number of twins and single-egg twins account for 1/3. What do twins look like in their mother’s belly? The [living conditions] of the baby in the mother’s belly are general, and Read More …