Abstract: A base unit for use in forming a molecular model has a polyhedral body having a first set of faces defining a plurality of first attachment surfaces, and a second set of faces defining a plurality of second attachment surfaces. A first set of the plurality of second attachment surfaces has a North magnetic polarity, and a second set of the plurality of second attachment surfaces has a South magnetic polarity. The base unit is magnetically coupleable to another base unit in a first configuration in which rotation of the base unit relative to the another unit is inhibited, and in a second configuration in which rotation of the base unit relative to the another unit is not inhibited.