Understanding the internal organization of cells from the molecular up to organelle level is a current challenge for biology if we are to better comprehend the mechanisms by which cellular processes occur. A prevailing view of the cell interior is that biochemical reactions and molecular movements are dominated by random diffusion. However, in addition to being compartmented into organelles, cells may well be organized at a finer level. Proteins may localise to specific areas within sub-cellular compartments, by associating with each other, the cytoskeleton and organelle membranes. Thus giving rise to distinct microcompartments. Considerable in vitro evidence exists for such interactions between enzymes and larger cellular components. This strengthens the idea that cells may be microcompartmented. However, little in vivo evidence supports this hypothesis, especially in plants. As a test-case for the concept of microcompartmentation this project investigated the sub-cellular distribution of the glycolytic enzyme fructose-bisphosphate aldolase in Arabidopsis thaliana; the ultimate aim being to establish whether it is microcompartmented in vivo and, further, to test the potential function(s) of such microcompartmentation.