The organ that is behind the belly button is the large intestines and the small intestines.
The jejunum and the ileum which are parts of the small intestine, lie directly behind your belly button.
And the large intestine also called the colon and transverse colon pass horizontally across your abdomen, behind your belly button.
The pancreas which is an organ also is situated deeper in your abdomen and is located behind your stomach and small intestine.
The exact location of these organs can also vary depending on the individual.
The belly button is where the umbilical cord was tied too which connected you as a fetus in your mothers womb to your mothers placenta to give you nutrients, vitamins and minerals to you, when you were in your mothers womb.
The umbilical cord tied to your belly button was essential while in the womb but the belly button has no functional purpose after birth.
The belly button is where the umbilical cord was tied off after birth and is simply a scar tissue remnant of the umbilical cord.
During fetal development, the umbilical cord connected you as a baby to the placenta providing the nutrients and oxygen you needed and in adults the belly button is not connected to any internal organs or structures and is now just a surface scar.