A microorganism is an organism that is too small to be seen with the unaided eye, such as bacteria, viruses, fungi, and protozoa. Microorganisms play an important role in the environment by breaking down organic matter, cycling nutrients, and providing food for other organisms. A macroorganism, on the other hand, is an organism that is visible to the naked eye, such as plants, insects, and animals.

A physical change is a change in the state or appearance of a substance, but the identity of the substance remains unchanged. Examples of physical changes include changing the shape of a solid, changing the state of a substance from a solid to a liquid, or changing the temperature of a substance. A chemical change, on the other hand, results in a change in the chemical identity of a substance. Examples of chemical changes include burning, rusting, and combustion.

Quantum mechanics is a branch of physics that deals with the behavior of matter and energy at the subatomic level. It is based on the principle that the energy of a system is quantized, meaning that it can only take on certain discrete values. Quantum mechanics studies the behavior of particles such as electrons, protons and neutrons, as well as the interactions between them.