Most common diseases and human traits have a multifactorial etiology with strong genetic contribution. The aim of our research is to identify genetic risk factors from the entire allelic spectrum, i.e., rare variants with strong effect sizes as well as common risk variants that modestly contribute to an individual's risk profile, for complex human traits. We use state-of-the art genomic technologies such as array-based genotyping, exome-/genome sequencing or multi-omics data generation in large cohorts. Our group has identified numerous risk factors for congenital defects such as orofacial clefting and, recently, host genetic factors involved in COVID-19. We also study the functional impact of variants which often provide their biological effect only in cell-type-specific and genomic context. Integrating multi-omics data across many biological layers, including genetic information, will be required to fully understand the biological mechanisms underlying common diseases.