Substellar research is a field of study that focuses on objects that are smaller and less massive than stars, but larger and more massive than planets. This includes brown dwarfs, which are often considered "failed stars" as they do not have enough mass to sustain nuclear fusion in their cores. Substellar research involves studying the physical properties, formation mechanisms, and evolution of these objects, as well as their potential impact on our understanding of star and planet formation. This field of research is important for helping us better understand the full range of objects that exist in the universe.