Rare Earth Elements (REE) are a group of 17 metals critical to modern technology.
They are irreplaceable in electronics, where europium is used in screens and neodymium in magnets. Electric vehicle motors rely on the REEs dysprosium and terbium. In defense, precision-guided munitions, radar systems, and night vision goggles use yttrium and lanthanum. Even LED bulbs depend on europium and yttrium. Medical MRI contrast agents and cancer treatments require gadolinium. They also are used as catalysts in chemical reactions for petroleum refining and catalytic converters.
REEs were formed during the cooling and solidification of the Earth's crust, primarily from igneous rocks such as granite and syenite.
Humans have known about REEs for 238 years. Significant advancements in understanding REEs occurred during the 20th and 21st centuries.