make structural-based color filters a promising choice for potential future opticsbased applications.In the area of flexible electronics, a number of flexible color filters have recently been reported utilizing either thin-film layer stacks or nanostructures. [15][16][17][18] These flexible filters are generally fabricated on plastic substrates such as polyethylene terephthalate (PET) that are hundreds of micrometers in thickness, feature millimeter to centimeterscale bending radii, and demonstrate little change in transmittance after repeated mechanical bending. Flexible filters can be suitable for a wide range of potential uses where an unusual form factor is required, or even integration with wearable devices. As an example, there have been previous reports of sensors either reliant on optical phenomena or containing simple optical elements that are demonstrably flexible enough to adhere to human skin. [19][20][21] Such devices would require any integrated components to have similar or better mechanical properties in excess of those possessed by current flexible color filters. One important factor to consider is conformal adhesion to a complex surface. Decreasing the film thickness generally results in decreased bending stiffness, allowing for greater adhesion to the surface. [22][23][24][25] To accomplish this, the thickness of the substrate layer can be decreased. Indeed, increased conformity while preserving filter effectiveness would be highly conducive for applications like on-skin pulse oximeters or wearable/implantable imagers where such characteristics are necessary. [26][27][28] Based on these requirements, in addition to flexibility an ideal color filter would also need to simultaneously be ultrathin and stretchable for sufficient mechanical compatibility.Herein, we demonstrate ultrathin, stretchable, and flexible structural color filters based on a simple metal-insulator-metal (MIM) structure on a 1.3 µm ultrathin substrate. We first fabricate silver-silicon dioxide-silver (Ag-SiO 2 -Ag) structures on top of ultrathin parylene substrates and characterize their basic optical and mechanical characteristics. We next investigate how effective the color filters are at both passing the desired wavelengths of light and blocking the undesired wavelengths of light both before and after mechanical deformation. We also describe the angular sensitivity of the color filters and assess its overall impact on filter performance. Remarkably, we find Color filters play a big role in a large number of modern technologies such as displays, sensors, and photovoltaics. In particular, structural color filters possess a number of advantages like high tolerance to heat, resistance to photodegradation, and long-term stability that make them a promising choice for potential future optics-based applications. In the field of flexible electronics, there are many sensors either reliant on optical phenomena or containing simple optical elements that are demonstrably flexible enough to adhere to uneven, deformable surfaces. Such de...