Learning many physics and chemistry concepts is much easier if it's done in a practical manner. But it isn't always possible to access a lab in which we have the material and tools necessary to carry out these experiments.
The dream come true for all physics, chemistry and science enthusiasts
That's the reason why the University of Colorado has developed PhET, a pack of utilities developed in Flash and in Java, and has included them in a very intuitive application so that both students, as well as teachers and science enthusiasts alike, can satisfy their curiosity in this matter without having to visit a lab.
Thus, PhET provides us with a pleasant environment to be able to experiment and carry out all kinds of simulations in a graphical and interactive manner. Once that application is installed it will be possible to access a complete collection of scientific experiments about all different matters, without requiring an Internet connection. The subjects covered are arithmetics, maths, electronics, kinematics, quantum physics, biology...