Visualizing biochemical activities in living cells.

Autofluorescent proteins have become indispensable in our quest to visualize molecular events in living cells. Further progress in the visualization and quantification of all biochemical activities of the cell will require the introduction of additional and complementary methods for sensing and probing biomolecules. Here I highlight some of the areas where the development of new probes and labeling methods is eagerly awaited and where chemical biologists could make important contributions.