In the moments immediately following the Big Bang, the universe rapidly expanded and then cooled down. This rapid cooling may have resulted in the creation of topological defects, which can be seen as remnants of the past. By studying the behavior of these defects in a computer model, we can gain insight into the early stages of the universe’s formation. In this chapter, we will present the numerical results of a simple model for topological phase transitions mediated by loops, and discuss its relevance to cosmic phase transitions.