decrease in temperature and disorder, composite fermions exhibit integer quantum Hall effect. The integer fillings of composite fermions, , correspond to the electrons fillings Combined with which are obtained by attaching vortices to holes in the lowest Landau level, these constitute the prominently observed sequences of fractions. Examples are The fractional quantum Hall effect of electrons is thus explained as the integer quantum Hall effect of composite fermions. It results in fractionally quantized Hall plateaus at with given by above quantized values. These sequences terminate at the composite fermion Fermi sea. Note that the fractions have odd denominators, which follows from the even vorticity of composite fermions. Fractional quantum Hall effect The above sequences account for most, but not all, observed fractions. Other fractions have been observed, which arise from a weak residual interaction between composite fermions, and are thus more delicate. A number of these are understood as fractional quantum Hall effect of composite fermions. For example, the fractional quantum Hall effect of composite fermions at produces the fraction 4/11, which does not belong to the primary sequences. Superconductivity An even denominator fraction, has been observed. Here the second Landau level is half full, but the state cannot be a Fermi sea of composite fermions, because the Fermi sea is gapless and does not show quantum Hall effect. This state is viewed as a "superconductor" of composite fermion, arising from a weak attractive interaction between composite fermions at this filling factor. The pairing of composite fermions opens a gap and produces a fractional quantum Hall effect. Excitons The neutral excitations of various fractional quantum Hall states are excitons of composite fermions, that is, particle hole pairs of composite fermions. The energy dispersion of these excitons has been measured by light scattering and phonon scattering. Spin At high magnetic fields the spin of composite fermions is frozen, but it is observable at relatively low magnetic fields. The fan diagram of the composite fermion Landau levels has been determined by transport, and shows both spin-up and spin-down composite fermion Landau levels. The fractional quantum Hall states as well as composite fermion Fermi sea are also partially spin polarized for relatively low magnetic fields. Effective magnetic field The effective magnetic field of composite fermions has been confirmed by the similarity of the fractional and the integer quantum Hall effects, observation of Fermi sea at half filled Landau level, and measurements of the