Learning can be a very complex set of processes. In a published in 1998, Petri and Niedderer explored how a student’s understanding of a key science concept, the atom, developed over time. They reported that the student’s conceptualization passed through a number a number of stages, but that the student actually operated with a mixture of the different versions of the concept, rather than cleanly moving moving on from one to the next. In their paper, “the student’s learning pathway is described as a sequence of several meta-stable conceptions”, and they found the student’s notion of the atom after teaching seemed to be a complex entity- “an association of three of three parallel conceptions” (Peri & Niedderer, 1998, p. 1075)