0 a situation in which an action or change that does not seem important has a very large effect, especially in other places or around the world:
Chaos theory relies on the idea of the "butterfly effect", that even slight imbalances in starting conditions lead to huge final variations in outcome because of the fundamental instability of the system.
And so we had the butterfly effect that was US households defaulting on their loans quickly causing chaos around the world.
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.