English: Proteins that function as morpheeins are illustrated using a dice analogy where one die can morph to two different shapes, cubic and tetrahedral. The illustrated assemblies apply a rule that the die face with one spot must contact the die face with four spots. To satisfy the rule for each die in an assembly, the cubic die can only form a tetramer and the tetrahedral die can only assemble to a pentamer. This is analogous to two different conformations (morpheein forms) of a protein subunit each dictating assembly to a different oligomer. All dice in one assembly must be of the same shape before assembly. Thus, for example, the tetramer must come apart, and its component dice must change shape to a pyramid before they can participate in assembly into a pentamer.