  We present the Period-Luminosity relations from 290 Cepheids towards the LMC
and 590 Cepheids towards the SMC. The two data sets were obtained using the two
wide field CCD cameras of the EROS 2 microlensing survey. We observe a
significant slope change of the period-luminosity relation for the SMC
fundamental mode Cepheids with periods shorter than 2 days. Many possible
experimental biases have been investigated, but none can account for this
effect. We also observe different spatial distributions for SMC Cepheids with
different ages i.e. periods. Different possible explanations of the slope
change are discussed.
