Yes, electronic devices can charge their batteries through various methods without being plugged into a source of electricity. What all the different methods have in common is that they absorb energy that is in some other form (heat, light, vibrations, radio waves, etc.) from the external environment and then convert the energy into electrochemical energy that is stored in the device's batteries. While such methods are scientifically sound and have already been successfully demonstrated, the energy captured from the outside environment is often not enough to be practically useful. Intense research is currently underway to make energy capture more efficient, and breakthroughs are beginning to be achieved in this area. Many phones are already available that offer wireless charging. Let us look at the main types of energy a device can use to charge itself without being plugged in.