Laser probe 40Ar/39Ar age dating can be applied in two ways. One is in situ spot age dating of a thin section using a pulsed laser, and the other is stepwise heating of a single mineral using a continuous laser. In the last 10 years, advances in technology have allowed us to apply the laser probes in various ways in Earth and planetary sciences. Stepwise data provide diffusion characteristics in each single mineral. The spatial resolution of laser pits can be as small as 5 microns, which is comparable to the figure for electron probe microanalysis. Utilizing this high resolution, 40Ar/39Ar applications combined with petrology are expected to contribute to a new understanding of argon diffusion and the Earth's history.