In this talk, we will review the identical spin rotation effect (ISRE) at the microscopic origin of many collective spin phenomena in cold atomic gases. The ISRE occurs during the collision between two indistinguishable atoms with internal levels (pseudo-spin). It leads to the appearance of an exchange mean-field term in the kinetic equation. The latter leads to phenomena such as spin waves, anomalous segregation between internal levels, spin synchronization in atomic clocks, etc. The consequences of ISRE have mainly been studied for non-condensed Bose or Fermi gases. However they are also expected to be important for partially condensed gases.