sentence2_structure: objects<>are<>atomic/subatomic$$$The specialized study of the motion of objects<>is called<>quantum mechanics
sentence1: Classical Mechanics, the behavior of objects of macroscopic size, can be explained as a special case of Quantum  Mechanics, although in practice Classical Mechanics was understood first.
sentence2: The specialized study of the motion of objects that are atomic/subatomic in size is called quantum mechanics.
question: The specialized study of the motion of objects that are atomic/subatomic in size is called what?