Historically, observations of the spectra of simple atoms have led to much of our understanding of the laws of physics. Recently, with tunable lasers, we are able to extend these observations with enormously increased resolution, sensitivity, and precision. There are a number of methods for overcoming the Doppler broadening of spectral lines. As little as a single atom can be observed and studied, by resonance fluorescence or photoionization. Complex spectra can be simplified in systematic ways by laser labeling of chosen levels. These and other advances in techniques are being applied to improve the measurement of fundamental constants, and to test the basic laws of physics.