We are continuing our exploration of the relationships between mechanics and kinematics. We have been investigating pairs, trios, and now quartets. Pairs gave us regimes. For trios, the outcome in the kinematic plane depended on the configuration of the trio in the mechanical plane: when the mechanical quantities are non-aligned, they produce events, where three regimes meet, as discussed in Episodes 9–11; when the mechanical quantities are aligned, they produce three parallel regimes, as discussed in Episodes 12–13. 

For quartets, we have seen that we obtain what we called "domains"—networks of connected events. So far, we have been focusing on two cases: explosions and capillary flows, with markedly different configurations, or different “topologies.” Today, we establish the existence of six different topologies for domains, depending on the relative dimensions of the four mechanical quantities in the quartet.