Most of the time, an embryo growing in the womb fully
develops into either a male or a female with all the
appropriate body parts and, many scientists believe, a
mindset programmed according to its gender. What determines
its gender—in most cases—are its sex
chromosomes: two X chromosomes in the nucleus of its
original egg cell and it will become a female; a Y and an X
chromosome and it will become a male. But exactly what
happens in the womb to make a boy or a girl? This
interactive feature illustrates the astonishing changes that
occur during the first 16 weeks of development.
Flash is a plug-in that allows for increased
interactivity. If you can see the animated boxes at left,
the plugin is already installed. If you do not see the
boxes, you can
install the Flash plugin, or select this feature's non-Flash version.
