Inventory in RPGs

Hmm…
I was wondering how you could make an inventory, so you pick up items and you place it in the inventory, so you can use it in battles. The battle system is in a different scene.

So in other words :

How do you pick up items and look at them in a special screen like “pack” or “inventory”, and how do you put items somewhere in the “Main” scene, and transfer it to the “Battle” scene?

Thx.

P.S : I think Templarian should reply this, coz in his “Little Game” there was an inventory in one of those screenshots. But if you know, please reply this too!