The postbasal, antemedian, median, postmedian and subterminal bands are formed by an alignment of white spots underlined with brown and intercalating between veins.
In the laboratory the intercalating properties have long been used to minimize chromosomal condensation when a culture is exposed to mitotic arresting agents during harvest.
The companies take the same basic manufacturing approach, which is to break apart graphite into the sheets of graphene that make it up -- usually by intercalating acids between them.
It is one of many examples of leap week calendars, calendars which maintain synchronization with the solar year by intercalating entire weeks rather than single days.