This document describes systems for in vivo light delivery that are inexpensive and relatively easy to use.  The goal is to provide the least expensive, most current, helpful information about systems you can use for in vivo optical neuromodulation.   We will try to update this document every few months, so that what you see below represents the best practices of the field.  Please note, part numbers for products are liable to change at any time; contact the manufacturer for updates, and please notify the authors of this white paper as well.  Feedback always welcome!