Models are numbered and can be sorted in a folder for easy viewing 1 - a simple x=1 model, with no units About the simplest CellML model one could come up with that actually has some maths. 2 - a simple association reaction with units, including some derived from new units. 3 - as 2 but the law of mass action has been abstracted into a separate component 4 - as 3 but the components are in separate files and therefore this uses imports. 5 - as 4 but includes 2 association reactions each obtaining their equation from the child component. So uses encapsulation etc too 6 - as 5 but abstracts the data (parameter values) out of the components into a separate component