When atoms and molecules are excited by ultrashort laser pulses, highly nonlinear strong-field processes like above-threshold ionization and high harmonic generation occur. By analyzing the emitted light and electron signals, the atomic and molecular structures and ultrafast dynamics can be detected with a combination of Angstrom spatial resolution and sub-femtosecond temporal resolution, which provides a powerful tool to study the basic structures and physical processes in the microscopic world. The molecular orbital tomography (MOT) developed since 2004 enables one to image the wavefunction of the molecular orbital itself, which will help people gain deeper insight into the chemical reactions. In this paper, the theory of MOT will be introduced, and the progresses of MOT in the past ten years will be reviewed.