Mass spectrometry remains a highly sensitive and efficient instrumental analytical technique known for its ability to determine molecular mass, provide structural insights, and enable quantitation. Developed over a century ago, it continues to evolve in terms of sensitivity and application across diverse scientific and technological domains. Mass spectrometry's capabilities extend to studying macromolecules such as proteins and protein complexes, with sensitivity reaching levels as low as atto- or zeptomoles. Coupled with separation techniques, it can analyze complex mixtures and trace-level compounds in biological matrices like active pharmaceutical ingredients and metabolites. Recent advancements have propelled proteomics research as a significant frontier. This review briefly introduces fundamental mass spectrometry techniques and tandem mass spectrometry.