Abstract: Chemistry begins with the motion of electrons. We study this motion on its natural time scales—from femtoseconds to attoseconds, among the shortest events ever measured. Using ultrashort laser or x-ray laser pulses, we can both observe and manipulate electrons and atoms as molecules change, allowing us to watch the first steps of chemical reactions unfold. By using very intense laser fields, we can even direct electron motion in ways that are impossible under ordinary conditions. These experiments produce "molecular movies" that reveal quantum dynamics in real time and help us understand how light controls matter at its most fundamental level.