U ovom radu prikazan je način rada lasera te njegova primjena u znanosti i tehnologiji. Kroz fenomen stimulirane emisije pobliže je opisan utjecaj fotona na elektrone u atomu te su razloženi uvjeti koji dovode do ostvarenja inverzije napučenosti, fenomena koji je ključan za razumijevanje principa rada lasera. Opisane su ključne komponente lasera i njihovo djelovanje u sklopu sustava te je prikazana razlika u načinu rada kontinuiranog i pulsnog lasera. Navode se mnogobrojni primjeri uporabe lasera u znanosti i objašnjavaju načini djelovanja te se ističe prednost korištenja lasera pred drugim metodama. Opisani su i glavni industrijski laseri i režim rada te je prikazano područje njihove primjene. Prikazane su neke od važnijih primjena lasera u znanosti te je u kratkim crtama objašnjen način djelovanja u tim metodama. In this paper, the mode of operation of the laser and its application in science and technology are presented. Through the phenomenon of stimulated emission, the influence of photons on electrons in an atom is described in more detail, and the conditions that lead to the realization of population inversion, a phenomenon that is crucial for understanding the principle of laser operation, are explained. The key components of the laser and their operation as part of the system are described, and the difference in the mode of operation of continuous and pulsed lasers is shown. Numerous examples of the use of lasers in science are given and methods of action are explained, and the advantage of using lasers over other methods is highlighted. The main industrial lasers and their mode of operation are also described, and the area of their application is shown. Some of the more important applications of lasers in science are presented, and the mode of action in these methods is briefly explained.