eye-opener
noun [ C usually singular ] uk/ˈaɪˌəʊ.pən.ər/ us/ˈaɪˌoʊ.pən.ɚ/
使人大开眼界的事物；有启发性的东西
something that surprises you and teaches you new facts about life, people, etc.
Living in another country can be a real eye-opener. 在外国生活确实可以令人大开眼界。