This is a set of interactive Java applets illustrating time dependence and superposition in one-dimensional quantum states. Simulations are used to illustrate the time dependence (real and imaginary parts) of eigenstates states, and superposition of eigenstates. There is an application of these ideas to a two-level model of an ammonia molecule. There is also an illustration of a harmonic oscillator with multiple states occupied, and coherent states. These applets are part of an extensive collection of animations and simulations illustrating a large range of quantum topics, and an ongoing effort for developing a fully interactive quantum-physics class.  Both French and English versions are available.