The field of cell biology is wide and deep, just like the functioning of cells. There are almost countless tools from which to choose, whether you use cultured cells, which may require passaging or expansion, or primary cells that use tools for dissection and cell isolation. Microscopes for viewing cells and their intracellular milieu are essential. Today’s microscope imaging systems and digital cameras extract more imaging data than ever before. Cellular images can be collected and analyzed using high-throughput screening systems, high-content screening/analysis systems, or flow cytometry systems. Usually, such methods depend on fluorescent probes and dyes, of which there has been an explosion of variety in recent years. Other tools are useful for keeping tabs on the health of cells, such as cell counters, and assays for cell viability, cytotoxicity, and apoptosis. Pumps and/or perfusion systems are often used to maintain cells (and to apply drugs or other compounds at particular time points) when not in incubators, such as when being studied under the microscope or imaging system. Studying signal transduction within and between cells benefits from assays for G protein functions, kinases, ligand binding, and receptor membrane protein activity, to name a few. Other readouts used in cell biology include Western blot analysis, ELISAs, and ELISPOT assays. Molecular biological tools are also valuable in cell biology to alter cellular function, such as the introduction of siRNAs or viral vectors.