A structure is composed of substructures. As large as galaxy, it is made of fundamental particles. Size, shape, and composition of structures can be different, however, I believe the fundamental principles has to be the same from micro to macro scale.

Universe starts from fundamental particles with perfect honesty and commitment. Micro events happen in light speed, and macro events can take billions of years. Galaxy is a superset of collections including other black holes, solar systems, star, plants, and all alike. The properties of particles and substructures are incorporated in the structure. We are not mystified by the making of duct particle or rock. Making of a star, black hole, solar system, galaxy, or cluster of galaxies should not be mysterious force that we can not comprehend. Any interpretation shall not be illogical, paradoxical, mind-boggling, or specious of any kind.

It's unlikely we will discover all type of galaxies. The diversity of life on a small planet Earth is far excess our imagination. I believe the universe using the fundamental particles can build structures that will continue on surprising us. So far, what we have observed is less of a blink of eyes.