Charles started out in Paulsson lab working on theoretical problems related to limits on oscillatory biological systems, such as the well known repressilator. However, he began to have a change of heart and started working as an experimentalist. Since then, he had been working with Somenath Bakshi and Emanuele Leoncini on developing a method to study bacterial adaptation at the single cell level. He then had begun looking at the distributions of low copy plasmids in single cells.