Applied Energistics 2 is a mod that focuses on creating a compact, easily accessible, considerably expandable and extendable storage system called a ME Network. The "ME" in the title stands for "Matter <-> Energy" - the premise being that items added to the system are converted into energy and stored in a digital energy form before needing to be used again, whereupon they are converted back into matter.

 

DrShnig has made a tutorial about Applied Energistics 2 that I highly reccomend you check out.

 

I'll save you some time and give you the tutorial right here!