MOSFET scaling continues to take transistors to smaller and smaller dimensions. Today, the MOSFET is a true nanoelectronic device – one of enormous importance for computing, data storage, and for communications. In this lecture, I will present a simple, physical model for the nanoscale MOSFET using the ideas and approach introduced in Prof. Datta’s first lecture. Surprisingly, we will find that the smaller MOSFETs become, the easier they are to understand. The first part of the lecture will develop the model starting from Prof. Supriyo Datta’s general model for a nanodevice. In the second part, we will do the same thing using more traditional approaches from semiconductor electronics. Hopefully this approach will help students understand how the “bottom up” and “top down” approaches relate. This lecture will also provide an entry point into a more extensive tutorial on nanotransistors that is available online as the short course Physics of Nanoscale MOSFETs.