Capsules are the latest in dwarven technology, it's an advanced storage method. Can store inside items, blocks(placed in the world) and even some entities.
To store entities just right click on them. Most of the animals can be stored in a capsule, and also mecha golems .
To store blocks you will need a storage station placed in the world, there are diferent sizes of stations. Left click on the station with the capsule in hand to store in the capsule the blocks(and entities) inside the station bounding box.
To release the contents in the world just right click with it on the place you want your contents delivered.