The fetal stage commences at the beginning of the 11th week.[2] At the start of the fetal stage, the fetus is typically about 30 mm (1.2 inches) in length from crown to rump, and weighs about 8 grams.[2] The head makes up nearly half of the fetus' size.[9] Breathing-like movement of the fetus is necessary for stimulation of lung development, rather than for obtaining oxygen.[10]The heart, hands, feet, brain and other organs are present, but are only at the beginning of development and have minimal operation.