New low frequency ac susceptibility measurements on two different spin glasses show that cooling/heating the sample at a constant rate yields an essentially reversible (but rate dependent) χ( T ) curve; a downward relaxation of χ occurs during a temporary stop at constant temperature ( aging ). Two main features of our results are (i) when cooling is resumed after such a stop; χ goes back to the reversible curve ( chaos ); and (ii) upon reheating; χ perfectly traces the previous aging history ( memory ). We discuss implications of our results for a real space (as opposed to phase space ) picture of spin glasses.