Crystal Heart

Crystal Hearts are objects found on any layer below the surface. When the player breaks a Crystal Heart using a Hammer, or explosives, it drops a Life Crystal which can be picked up. The life crystal can be used to increase your maximum health by 1 heart (or 20 HP). It also heals you by the same amount.

It should be noted that crystal hearts can be easily found in the Dungeon, or in The Underworld, and once your MaxHP reaches 400 theres no need for crystal hearts, unless you have more than one character, even then when that ones at 400/MaxHP theres no need for them. They can't be used for decoration, unless you wanna build a house around the heart...