The aim of the research project is to analyze and describe how pre-school teachers during an in-service training period develop theoretical knowledge about focusing the content when planning for teaching science in pre-school. The variation theory is used for analysis as well as for the planning for teaching in pre-school. The theory can be described in terms of learning object, critical aspects, discernment, simultaneity and differences. 30 pre-school teachers from nine different municipalities participated in the project. The empirical material consists of a questionnaire as the preschool teachers answered in the beginning and in the end of the training period and of group reports. The results can be discussed as a number of critical aspects in relation to teachers'learning as: ways of understand the concept of variation, to discern the object of learning and to discern o shared space of learning.