Measurements at the single-entity level provide more precise diagnosis and understanding of basic biological and chemical processes.Recent advances in the chemical measurement provide a means for ultra-sensitive analysis.Confining the single analyte and electrons near the sensing interface can greatly enhance the sensitivity and selectivity.In this review,we summarize the recent progress in single-entity electrochemistry of single molecules,single particles,single cells and even brain analysis.The benefits of confining these entities to a compatible size sensing interface are exemplified.Finally,the opportunities and challenges of single entity electrochemistry are addressed.