Lasers are useful for spectroscopy and microscopy in science. In my lab, we use lasers to excite fluorophores (such as a green fluorescent protein) and image them in cells. More complicated applications involve using a pair of fluorophores as a spectroscopic ruler (Förster resonance energy transfer or FRET). Lasers can also be used for micromanipulation of chemical or biological systems. In these experiments, called optical tweezing or laser tweezing, one traps a bead in the focus of a tightly focused laser beam. If this beam is attached to a molecule or interest, one can move the beam in order to pull on and exert force on that molecule. Such experiments have been used to study the elasticity of DNA and even to look at the ability of molecular motors (such as DNA polymerase, the enzymes involved replicating DNA) to generate force.