Patterns in permaculture
The universe is full of patterns that repeat themselves in different places: the branching structure of trees looks exactly like the human lung, foam floating on water forms shapes identical to galaxies and also to cyclones, your brain cells look like the universe.
These patterns emerge from the chaotic interaction of two forces, such as a river pushing against its bank or two fronts of air meeting each other. Considered with an ecological attitude, the benefit of a system comes not so much from the, but rather from the connections between them. These interactions happen at edges, where two substances or two forces meet each other. Choosing the right pattern for an edge in the permaculture system (like the edge of a pond on the farm) can enhance the interactions between elements and lead to a more productive, healthier system.
- Keyholes. 
- Concentric circles