Given the task definition and input, reply with output. Given a scientific passage and an answer, generate a question for the given answer.

Passage: After equilibrium has been reached, the concentrations of all reaction components will remain constant unless a change is made to the system. Because the concentrations are no longer changing, it may appear that the reaction has "stopped. " This is incorrect; both the forward and reverse reactions are still going on, even at equilibrium. However, because the two reactions are proceeding at the same rate, no net change is observed. Answer: equilibrium
After what state is reached, the concentrations of all reaction components remain constant unless a change is made to the system?