This article is a discussion drawing on a learning study with a teacher working with one- and two-year-olds. The focal interest is a scrutiny of the use of manipulative objects, emanating from observations of a teacher's and children's use of, and responses to the use of, different objects. The concept of size and the notions 'large' and 'small' are offered as authentic examples and analysed in terms of the variation theory of learning. Main findings are that mathematics learning in early childhood will benefit from a greater attention to how teachers can make use of specific objects for certain pedagogical purposes. Analysis reveals the necessity to pay attention to how the aspects of the learning object can be discerned by the children, given that fewer features offer more learning opportunities. The teacher's role as a guide is, though, considered essential in supporting the children's discerning act through both verbal and visual means. (author abstract)