An electrode configured to provide electrical contact with a subject's skin and includes a conductive layer and a gel layer. The conductive layer spreads current and transmits electrical signals to and/or receives electrical signals from the subject's skin and has a first conductive surface through which electrical signals are transmitted to and/or received from the subject's skin. The first conductive surface is on a side of the conductive layer that faces toward the subject's skin if the electrode is installed on the subject. The gel layer is formed on the same side of the conductive layer as the first conductive surface. The gel layer has a first interface surface that directly contacts the subject's skin if the electrode is installed on the subject, and to conduct electrical signals between the subject's skin and the first conductive surface. The first interface surface has a surface area larger than that of the first conductive surface.