Optogenetic experiments rely on the controlled delivery of light to diverse biological systems. Impressive devices have been recently developed to stimulate cells and small animals with multiple wavelengths and intensities. However, existing hardware solutions are often limited to a single sample holder, and their design and cost can further limit scalability. This chapter describes an illumination system that is modular (through the use of accessible components) and scalable (through a shelving structure and low cost). Assembly and operation require no or minimal electrical engineering or programming expertise. Multi-intensity wavelength and temporal experiments can be performed in dozens of small and large samples. This chapter also introduces methods for temperature and light intensity measurements toward appropriate illumination conditions. This work aims to provide a greater level of accessibility and complementary opportunities for large-scale optogenetics in a broad range of biological samples.