When we develop our apps, we keep the cognitive abilities of children of every age group in mind. Children between the ages of 4 and 6 are developing a feel for time (‘yesterday’, ‘today’, and ‘tomorrow’) are becoming familiar with the idea of a sequence of events (‘first’ and ‘later’), can conjugate verbs in their past forms and correctly respond to questions on short stories. Apps that we develop for children of this age are tested by children of precisely this age until they are perfectly suitable for all pre-schoolers and are ready to be published.