For those who might now know, the last substantive update brought with it the ability to bring a "backpack" with you to substantially increase the amount of items you can carry along on your adventures. The "backpack" here is the enderchest. When you venture into the dark, deep below, bring an enderchest with you along with a pickaxe with the silk touch enchantment. This will take up two of your inventory slots, but they will give you so much more. To use your "backpack", place your enderchest on the ground, fill it (or remove items from it) and then break it with your silk touch-enchanted pickaxe and pick it up again. No matter how full the enderchest is, it will only take up one inventory spot. Bringing an enderchest with you almost doubles your inventory capacity.