Mechanochromic devices have remarkable capabilities to change transparency and/or colour in response to mechanical stimuli, making them attractive for a wide range of applications in smart windows, strain sensors, encryption, tunable wetting systems, between others. In fact, some marine life forms have evolved camouflage traits involving dynamic and reversible alteration of their transparency, fluorescence, and colouration via muscle-controlled surface structures and morphologies. A number of marine organisms use muscle-controlled surface structures to achieve rapid changes in colour and transparency with outstanding reversibility. Inspired by these display tactics, scientists have develop analogous deformation-controlled surface-engineering approaches via strain-dependent cracks and folds to realize the following four mechanochromic devices: (1) transparency change mechanochromism (TCM), (2) luminescent mechanochromism (LM), (3) colour alteration mechanochromism (CAM) and (4) encryption mechanochromism (EM). These devices are based on a simple bilayer system that exhibits a broad range of mechanochromic behaviours with high sensitivity and reversibility. The TCM device can reversibly switch between transparent and opaque states. The LM can emit intensive fluorescence as stretched with very high strain sensitivity. The CAM can turn fluorescence from green to yellow to orange as stretched within 20% strain. The EM device can reversibly reveal and conceal any desirable patterns.