Photoplethysmography (PPG) is a low-cost, non-invasive optical technique widely used in clinical settings and wearable devices, which is very up-to-date in cardiovascular diseases. This method is promising to test the level of lipid profile. This review aims to synthesize current evidence on the application of PPG in assessing atherosclerosis and its correlation with lipid profiles, while discussing the technological foundations and future directions of wearable cardiovascular monitoring. A narrative review was conducted based on a literature search of PubMed, IEEE Xplore, Google Scholar and Scopus databases. The analysis included studies focusing on PPG morphology, the physics of light-tissue interaction, and emerging technologies such as graphene-based sensors. The literature indicates that PPG signal morphology, particularly features related to pulse wave velocity and arterial stiffness, correlates with subclinical atherosclerosis. Recent proof-of-concept studies suggest that machine learning models can predict cholesterol levels from PPG features with increasing accuracy. The synthesis of PPG and smartwatches (or electronic rings) is prospective in medical diagnosis, e.g. arteriosclerosis, aging of vessels in real-time or LDL-cholesterol level. That light technic is a versatile technology that bridges the gap between engineering and clinical diagnostics. While it cannot yet replace laboratory blood tests, it serves as a powerful screening tool for early cardiovascular risk stratification. Future research should focus on refining multi-wavelength sensors and AI-driven data analysis.