Light is one of the most essential environmental factors affecting plant development and growth. Throughout the entire life cycle of plants, light mediates almost every stage of developmental processes. Plants have evolved a complicated but delicate light signal transduction network in response to dynamically changing light environment in nature. Over the past three decades, plant photobiologists have revealed a light signal transduction system, photoreceptors-E3 ubiquitin ligase complex-transcription factors. This regulatory network affects approximately one third of gene expressions throughout whole genome to ensure normal development in plants.