Fractals are any systems which has self-similarity properties. An Apollonian gasket or Apollonian net is a fractal generated by starting with a triple of circles, each tangent to the other two, and successively filling in more circles, each tangent to another three.
Apollonian Gasket provides a composition exercise which results in a fractal. It is packing of circles in a space created between circles. There are several ways to pack circles inside each other. For example, I have started with three circles and kept packing them in the spaces created between the triples of circles. It could be done on an infinite scale but I finished after certain magnifications. The end result creates a negative Space that has its own intricate geometry.