Intra- and Inter-tumoral heterogeneity is one of the main hurdles in diagnosing and treating breast cancer. Selecting, sampling, and sequencing the samples appropriately provide unique opportunities in realizing precision medicine. This chapter reviews some of the past landmarks, state-of-the-art technologies, and future directions of translational research in terms of tumor sampling technologies and sequencing in breast cancer. In the state-of-the-art technologies section, the technologies are categorized in terms of scientific, precision diagnostic, and precision therapeutic tools. Finally, limitations and future directions regarding various translational research for clinical applications using these technologies will be discussed.