Single-cell Raman spectroscopy is a noninvasive and label-free technology for biochemical analysis of bacterial cells. A single-cell Raman spectrum functions as a metabolic "fingerprint" of an individual cell, which enables differentiation of cell types, physiological states, nutrient condition, and variable phenotypes. Raman tweezers combines single-cell Raman spectroscopy with optical laser tweezers to allow the identification and isolation of single living cells according to their Raman spectra. After cell sorting subsequent culturing and genomic sequencing has the potential to reveal totally new groups of microbes. Stable isotope probing with Raman tweezers offers a culture-independent toolbox to study genetic functions and physiology of unculturable microorganisms in the ecosystem.