Neutron structure. Computer artwork showing the constituent parts of a neutron. The neutron is made up of three quarks (blue and white) held together by gluons (red). The quarks making up the neutron are the up quark (arrow up) and two down quarks (arrow down). The up quark has a charge of 2/3, and each down quark has a charge of -1/3, giving the neutron no overall electrical charge. The gluons have no charge.