We develop first-principles models of molecular spectroscopies that connect measured signals directly to molecular structure, dynamics, and electronic motion in complex environments. By combining molecular dynamics with quantum-mechanical response theories, we simulate a broad range of spectroscopies. These include vibrational linear infrared, two-dimensional (2D IR) and sum-frequency generation (SFG) spectroscopies to unravel molecular ultrafast dynamics in solution and at interfaces, attosecond pump–probe spectroscopies to probe electron and nuclear dynamics in connection with high harmonic generation, and vibrational circular dichroism (VCD) modeling to link chiral spectroscopic signatures to conformational fluctuations and solvation effects in solution.