There are many different types of matter in the universe. All of them are formed when various dimensional fields interact with each other. Some matter, such as short and normal, can interact with each other extremely violently. While others pass through each other as if neither exists.
All normal matter is four dimensional and is trillions of years in length. It was created when short matter joined end to end, creating longer and longer chains. The Lights noticed that all normal matter appears to start at the same time in a relatively close space and is held in place by various interacting fields. This point in time is referred to as the big bang by human, but in reality there was no sudden explosion and expansion of the universe. Our particular four dimensional space is warped by higher dimensions, making it appear to be expanding from a three dimensional point of view.
The material the Lights bodies are made from. Most extends six days along the time dimension, but that may be due more to the way the Lights constructed their bodies, than anything else. Short Matter can be caught up in a time wave the same way a mind can, which allows the Lights to easily travel along time observing all the organic life which exists that way.
An interesting aspect of short matter is that it reacts quite differently with normal matter than would be expected. The reason is because short matter will always try to connect to other short matter to make longer pieces. For example: If a piece of short matter iron come in contact with normal matter iron, it will split the normal matter into two pieces as it attempts to connect. A single atom of short matter would then connect to one of the two pieces it created. But when short matter is in a group, an iron crystal for example, nothing can be connected so it keeps interacting with the normal matter, tearing it apart and releasing huge amounts of energy.
Similar in size to short matter, but created by the interaction of other dimensional fields. Mind Matter is the most durable matter Lights know of. During their early existence, when matter was first forming, many Lights were curious as to what the star were. They journeyed extremely close, only to have their short matter bodies vaporized. Some shifted their minds into normal space to look for their bodies, but experience intense pain in their minds from the energy given off by the stars but no physical damage. Only the beings living n the Dren empty space have been known to have the ability to destroy mind matter. Everything else only seems to cause pain.