A novel mathematical approach has uncovered that some animal cells have robust 12-hour cycles of genetic activity, in addition to circadian or 24-hour cycles. The method, published in the journal PLOS ONE, assessed the periodicity of gene expression data and compared the results with those obtained with other computational methods. As opposed to the other methods, this novel approach showed not only the existence of unsuspected biological cycles, but also that the 12-hour cycles work independently from the 24-hour cycles, which has been confirmed by laboratory experiments. These findings open a new area of study of how gene functions over time influence health and disease.