A qualitative investigation of how undergraduate chemistry students used modeling clay to represent their submicroscopic conceptions of a formaldehyde molecule was undertaken. A total of 56 students participated in an open-ended, hour-long qualitative interview. Volunteers from the study were solicited from first-semester general chemistry, organic chemistry, inorganic chemistry, and physical chemistry courses. Results indicated that when students were allowed to build their own models without the restrictions imposed by conventional model kits, students built creative and unconventional models. The results indicated that students' submicroscopic representations are resistant to change, despite taking more chemistry classes.