Optical tweezers (in the past called "single-beam gradient force trap") is an instrument using a focused laser beam to attract or repel small objects.

Much like regular tweezers objects can be grabbed and moved using extremely focused light, but only on very small distances (micrometers).  

They are able to trap and manipulate small particles, typically order of micron in size, including dielectric and absorbing particles. Optical tweezers have been successful in studying a variety of biological systems like living cells, DNA and viruses.

The first report about the principles that led to the development of optical tweezers came from Arthur Ashkin, a scientist working at Bell Labs. He described the optical scattering and gradient forces on micron-sized particles and eventually, he won the 2018 Nobel Prize in Physics for his discovery.

In the late 1980s, Arthur Ashkin and Joseph M. Dziedzic demonstrated the first application of the technology to the biological sciences, using it to trap an individual tobacco mosaic virus and Escherichia coli bacterium.

The technique has countless applications: cell sorting, cell imaging, the study of molecules like DNA and enzymes, etc.