Crystal Heart

Crystal Hearts are objects found on any layer below the surface. When the player breaks a Crystal Heart using a pickaxe, drill, 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 health. It also heals you by the same amount. Crystal hearts cannot be used once the player has 400 health, where only Life Fruit can further increase the player's health to a maximum of 500.

While they can be hard to find, single-player mode worlds will actually contain dozens more Crystal Hearts than the player can use.