In traditional embryo selection by morphology, the embryologist observes certain aspects of embryo morphology at certain times during embryonic development.
These observations can only be ad hoc, as the embryo must be taken out of the incubator for observation and evaluation. This results in a change in the optimal culture conditions in which the embryo is inside the incubator.
However, time-lapse systems, such as the Eeva, allow the embryo to be observed during the entire period of embryo development without the need to remove it from the incubator. This is possible thanks to the incorporation into the incubator of an image capture system at a specific time interval.