A strong laser field can sometimes induce unusual phenomena that cannot be understood by treating the field as a perturbation. These "strong-field" phenomena, including above-threshold ionization and high-order harmonic generation, have been widely studied in atomic and molecular systems. Laser-driven solids are predicted to exhibit exotic phenomena that cannot be expected for atoms, but experimental realization has been hindered by unavoidable sample damage at high laser intensities. This talk will describe our recent observations of strong-field phenomena in semiconductors using intense mid-infrared radiation. The small photon energies minimize interband absorption and sample damage while the ponderomotive potential (or the 'wiggle' energy) for a given laser intensity increases quadratically with decreasing photon energy. We observed non-intuitive modifications of optical absorption and emission properties of various semiconductors in addition to harmonic generation up to 7th for the first time.