In this project, we propose the development of a new imaging modality, which would facilitate submicrometre-scale observations of fluorescence lifetime in deep brain regions of living animals. Exploiting the principles of holographic endoscopy, we will introduce the prospect of Fluorescence Lifetime Imaging Microscopy (FLIM) through hair-thin multimode fibres. The minimally invasive FLIM endoscope will offer microenvironment-sensitive imaging, ideal for probing dynamic molecular processes within deep-brain structures.