(color online) (a) Pump-probe spectroscopy performed with 390 nm pump and 660 nm probe on a mechanically exfoliated MoS₂ sample (transferred onto a SO₂/Si substrate), showing a carrier lifetime of .^[83] (b) Time-resolved differential transmission spectra performed on a liquid phase exfoliated few-layer WS₂ sample with degenerate 635 nm pump and probe beam, showing a fast PB signal (∼ 5 ps), followed by an emerging PA signature.^[84] (c) Transient differential transmission performed with 10 fs visible pulses on a few-layer MoS₂ sample grown by CVD method. Carrier thermalization occurs within 20 fs and the subsequent cooling of Fermi–Dirac carrier distribution occurs on the ∼ 0.6 ps timescale.^[85] (d) Pump–probe spectroscopy performed on mechanically exfoliated MoS₂ sample with 452 nm pump and 905 nm probe, showing the dependence of the timescales on the layer number. Different curves are scaled in magnitude for clarity.^[86]