Traditional reductionist approaches play a crucial role in our understanding of biology and medicine, but they cannot explain the full complexity of biological phenomena and human disease. Systems biology combines recent high-throughput profiling technologies—such as transcriptomics, proteomics, and metabolomics—with computational modeling to capture, summarize, and understand this complexity. In this article, we provide a detailed overview of these experimental profiling technologies and computational modeling approaches. Several case studies illustrate how system approaches are already effectively used in toxicology assessment, drug development, diagnostics, and personalized medicine. Overall, this article provides the foundations to further integrate systems biology approaches into biomedical research.