A more concentrated form of light was found during the 20th century: lasers. These were used to observe tiny molecules of gas, which allowed for understanding of particles such as electrons.
接著，本世紀初發現更純淨、亮度更高的雷射光，可被應用來研究、觀察更細微的氣體分子，以瞭解物質的微觀電子結構。