The structures that can be implemented and the materials that are used in complementary metal-oxide semiconductor (CMOS) integrated circuit (IC) technology are optimized for electronic performance. However, they are also suitable for manipulating and detecting optical signals. In this paper, we show that while CMOS scaling trends are motivated by improved electronic performance, they are also creating new opportunities for controlling and detecting optical signals at the nanometer scale. For example, in 90-nm CMOS technology the minimum feature size of metal interconnects reaches below 100 nm. This enables the design of nano-slits and nano-apertures that allow control of optical signals at sub-wavelength dimensions. The ability to engineer materials at the nanoscale even holds the promise of creating meta-materials with optical properties, which are unlike those found in the world around us. As an early example of the monolithic integration of electronics and sub-wavelength metal optics, we focus on integrated color pixels (ICPs), a novel color architecture for CMOS image sensors. Following the trend of increased integration in the field of CMOS image sensors, we recently integrated color-filtering capabilities inside image sensor pixels. Specifically, we demonstrated wavelength selectivity of sub-wavelength patterned metal layers in a 180-nm CMOS technology. To fulfill the promise of monolithic photonic integration and to design useful nanophotonic components, such as those employed in ICPs, we argue that analytical models capturing the underlying physical mechanisms of light-matter interaction are of utmost importance.