In our recently published paper we have described a genetically-encoded matrix metalloproteinase-9 (MMP-9) activity biosensor. MMP-9 is an extracellular endopeptidase known to cleave a number of proteins within the extracellular space and on the surface of cells. It plays a significant role in both physiological and pathological processes (such as the development of cancer). In the central nervous system it regulates the synaptic plasticity, the basis of memory and learning. MMP-9 activity biosensor enables the tracking of its activity with a very high spatiotemporal resolution and thus understanding its role in the pathophysiology of central nervous system. The biosensor is localized on the external leaf of the plasma membrane and utilizes the fluorescence resonance energy transfer (FRET). Proteolytic activity of MMP-9 leads to the cleavage of the biosensor between the blue fluorescent protein (mTFP1) and yellow fluorescent proteins (Venus) and the loss of FRET between mTFP1 and Venus, which leads to the increase in the fluorescence intensity of mTFP1. Our biosensor is the first published genetically-encoded and membrane-anchored MMP-9 activity tracker. The biosensor enables the study of the proteolytic activity of MMP-9 with high temporal and subcellular resolution at the precise region of MMP-9 action on the cell.