The waterflea Daphnia magna is a cyclical parthenogen, which means that parthenogenetic and sexual reproduction alternate during its lifecycle. When the environmental conditions are favourable, reproduction is solely parthenogenetic. At the end of the growth season, when the environmental conditions deteriorate, Daphnia switches to sexual reproduction which results in the formation of resting eggs.  A portion of these testing eggs will hatch during the next spring after a period of hibernation. The remaining portion will accumulate in the sediment and contribute to the formation of a resting egg bank. The hatching success in a zooplanktron egg bank tends to be very variable within and between populations. The hatching rate is often low and shows a tendency to decrease over time. General degradation of the eggs, as a result of aging, can often not account for this failure to hatch because a lot of eggs appear to be very well-preserved, even after several decades in the sediment. The eggs appear to be trapped in the diapause state and fail to respond to hatching stimuli. This observation suggests that failure to hatch could be explained by the degradation of specific components, crucial for the resumption of development. This study aims to acquire a better understanding of the cellular processes that control hatching and inhibit the hatching of old resting eggs. We will also examine how and to which extent variation in the biochemical composition of the eggs can explain the great variability of hatching success within and between populations.