What is it called when molecules spread from areas of high concentration to areas of low concentration in order to reach an equilibrium?

Question: What is it called when molecules spread from areas of high concentration to areas of low concentration in order to reach an equilibrium?

Options:

Cells
Diffusion
Digestion
Titanium

Correct answer:

Diffusion

Other game answers: Scrabble Pics Answersdeer hunter 2015, Trivia Crack answers.