Plants typically grow at high densities in agricultural and most natural systems, where they compete for light. Shade avoidance responses help plants to escape from shade, imposed by neighbors. We study how these responses are regulated and how they can be controlled. Briefly, multiple light cues, as well as mechanical signals, inform plants about the presence of neighbors. These signals activate a cascade of transcription factors, hormones and cell wall modifying proteins to enhance unidirectional cell expansion leading to shoot elongation. Major regulators include Phytochrome-Interacting Factors (PIFs; a group of bHLH transcription factors), auxin, gibberellins, brassinosteroids and XTH proteins. We implement this knowledge to understand shade avoidance, and to unravel how photobiological responses interact with other environmental challenges such as pathogen attack and abiotic stress.