Microtubules play a central role in many essential cellular processes, including chromosome segregation, intracellular transport, and cell polarity. As these dynamic polymers are crucial components of eukaryotic cellular architecture, we were surprised by our recent discovery that a common human genetic difference leads to variation in microtubule stability in cells from different people. A single nucleotide polymorphism (SNP) near the TUBB6 gene, encoding class V β-tubulin, is associated with the expression level of this protein, which reduces microtubule stability at higher levels of expression. We discuss the novel cellular GWAS (genome-wide association study) platform that led to this discovery of natural, common variation in microtubule stability and the implications this finding may have for human health and disease, including cancer and neurological disorders. Furthermore, our generalizable approach provides a gateway for cell biologists to help interpret the functional consequences of human genetic variation.