Galaxy interactions play an important role in galaxy evolution. Numerous studies have pointed out that interacting galaxies have unique characteristics in many aspects such as morphology, star formation, metallicity, AGN activity, and spin angular momentum. While the interaction-induced evolution is usually ascribed to the gravitational tidal effect of neighboring galaxies, recent studies have identified the potential significance of hydrodynamic processes during interactions in interstellar and circumgalactic media. In this talk, I will give a brief overview of this field and present our latest work on galaxy pairs, i.e., the early phase of galaxy interactions, based on both observations and simulations. Specifically, I will describe the two interesting phenomena discovered in galaxy pairs: the star formation enhancement and the spin-orbit alignment. I will also discuss some clues to hydrodynamic effects at work and why these effects deserve further attention in future studies.