Photomorphogenesis is the process by which plants grow and develop in response to light signals. This process is mediated by a sophisticated network of photoreceptors among which phytochromes play a key role. Phytochrome-mediated photomorphogenic responses are characterized by the complex variety of relationships between light input and physiological outputs, including germination, de-etiolation, shade avoidance, circadian rhythm, and flowering. Recent studies have resulted in several important advances, and have revealed the major consequences of phytochrome activity in terms of controlling protein subcellular localization, transcription, protein stability, and protein phosphorylation. In addition, many downstream components in the phytochrome signaling have now been identified, and a complex, highly regulated signaling network is envisaged. Here, we review the current knowledge about red/far-red photoreceptor phytochromes and provide a comprehensive summary of the phytochrome-mediated photomorphogenesis signaling network.