Abstract: | Discoveries of major importance in life sciences and preclinical research are linked to the invention of microscopes that enable imaging of cells and their microstructures. Imaging technologies involving in vivo procedures using fluorescent dyes that permit labelling of cells have been developed over the last two decades. Fibered confocal fluorescence microscopy (FCFM) is an imaging technology equipped with fiber‐optic probes to deliver light to organs and tissues of live animals. This enables not only in vivo detection of fluorescent signals and visualization of cells, but also the study of dynamic processes, such cell proliferation, apoptosis and angiogenesis, under physiological and pathological conditions. This will allow the diagnosis of diseased organs and tissues and the evaluation of the efficacy of new therapies in animal models of human diseases. The aim of this report is to shed light on FCFM and its potential medical applications and discusses some factors that compromise the reliability and reproducibility of monitoring biological processes by FCFM. This report also highlights the issues concerning animal experimentation and welfare, and the contributions of FCFM to the 3Rs principals, replacement, reduction and refinement. ![image](/cms/asset/4ea4a7bb-e559-43ed-83a3-372a27998477/jbio201900146-gra-0001.png) |