The vision of flexible electronics based on organic semiconductors is to enable lightweight, cost-effective, power-efficient, and versatile electronic devices that can support people in any aspect of life. However, horizontal transistor configurations face severe contact resistance and device integration challenges when targeting short-channel geometries, required to reach device operation above 100 MHz. Here we discuss the idea of employing vertical organic transistors - a structure that holds great promise for high-frequency applications as the channel length is defined only by the thicknesses of the layers in these devices (as low as 100 nm). As an archetype device, we focus on so-called organic permeable base transistors to explain the device physics and scaling laws of vertical organic transistors.