Here we report the discovery of ultrathin copper films electrodeposited at a heptane/CuSO4 aqueous solution interface. The films consist of two layers; one is a very thin layer growing along the organic side of the interface, and the other is an aggregate of dendrites growing from the organic-side layer into the solution bulk. The thinnest film obtained in this study is composed of only the organic layer less than 1 mum in thickness, and it is transparent. Here we discuss how the interface is associated with the growth of the deposit. (C) 2004 The Electrochemical Society.