Artificial Light at Night (ALAN) has revolutionized how we live, work, and play.  It enhances our modern lives, and few of us can imagine life without ample lighting available at the flip of a switch.  ALAN is a tool that provides many benefits, but as with any tool we need to pick the right tool for the job, use it properly, and put it away when we’re done.  LED lights are an engineering marvel -they’re efficient, long lasting, and come in a variety of hues, or Color Temperatures, from invigorating blue-white ‘daylight’ bulbs to cozy amber ‘warm white’ bulbs.  But there can also be a dark side lighting.  Excessive or inappropriate lighting, or light pollution, can cause real harm -harm to our health, to our environment, and to our communities.  In this series of short articles, we’ll learn what light pollution is, how it impacts our health and the environment, and learn some simple things we can do in our homes, businesses, and communities to help us enjoy light’s benefits will avoiding its potential harms.