Nowadays electronics are incorporated in most parts of daily life. Needless to say that this trend can also be seen from a critical point, but nevertheless it brought a lot of facilitation and benefits to simplify our tasks. Carrying more and more electronic gadgets with us raises the question: What can we do to better fit them to our needs? Today we have smartphones, MP3-players and similar stuff, but in future we might even talk about integration of circuitry directly into the human body. Objectively spoken, human or other mammal bodies can be seen as soft machines, soft robots, combining functions for actuation as well as sensing and data processing. Electronics in its common rigid form is a rather charmless option to be combined with the soft nature of human tissue. The need for electronics being able to deform and adjust to arbitrary surfaces is where stretchable electronics joins in. Stretchability enables a whole new kind of devices. Skin-like and large area sensor applications are intended to mimic the human skin enhancing possibilities in robotics and prosthetics. Beyond that the application of circuits to free-form surfaces enables novel designs and additionally has the capability to revolutionize medical prevention and rehabilitation. This work explores several concepts regarding their suitability for stretchable and deformable electronics. Besides the basics, another important part of work was the study of their implementation towards real life applications ranging from health monitoring to ultra-light and conformable power generators. Amongst other things, a concept for fully stretchable electronic circuits, which can be reversibly stretched for at least 10000 times has been developed and published in Advanced Materials.