Apparatus for real-time in vivo bioluminescence monitoring in a conscious small animal, comprising a light-tight enclosure (4) with a base (16), side wall (19) and cover (20) configured for housing the small animal such that it may move freely, a bioluminescence detector system (6) comprising a light detector (22) for detecting the light emitted by said small animal connected to a data processing system, and a life-sustaining system (8) configured for maintaining the small animal alive for a prolonged period of time spanning from a few days to a few weeks.