Coils are made of elastic materials formed into the shape of helixes which return to their natural length when unloaded. With its unique geometry, the helix coil structure is one of the most stretchable forms among all kinds of shapes in man-made systems and nature. I employed the coil mechanics to modern stretchable electronics to archive an extreme level of elastic stretchability, which cannot be accomplished with existing technologies. Compared to typical 2D filamentary serpentines fully bonded onto soft planar elastomeric substrates, the proposed 3D helix structures are designed to be uniformly bent with compressive buckling with minimally defined bonding sites. The constructed helix coil interconnections can be naturally deformed along the coil direction under tensile stress with minimal stress concentration. As a result, these structures exhibit extreme elastic stretchability up to ~100%. Currently, I am building extremely stretchable biomedical devices as a system-level demo.