Nobel Prize in Physics in 2023 was awarded for generation of attosecond (1 as = 10^-18 s) pulses of electromagnetic radiation and application of attosecond pulses in studies of electrons in condensed matter. I will show basic physical mechanisms leading to generation of such pulses and methods to characterize them. I also talk about some applications of attosecond pulses in basic research such as studies of dynamics of photo effect, etc.