Rare-earth elements (REE) refer to a group of 17 elements, including 15 elements of the lanthanide series (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) and the other 2 elements scandium (Sc) and yttrium (Y). These elements and their alloys & compounds are currently essential to many technologies, including electronics, metallurgy, water treatment, glasses & ceramics, toys, catalysis, polishing, paint dryer, and much more.