We have developed a new spectroscopic system that can measure transient absorption spectra and 3D shapes of target objects that are hidden in an opaque container such as a colored glass bottle, an envelope, and a plastic bag. Multiphoton excitation by a femtosecond near-infrared laser pulse, which easily penetrates into the opaque containers, can induce transient coloring of the target material, and the transient absorption spectra can be measured by the light pulse following the exaction pulse with a controlled delay time. Even 3D imaging of the object is possible when the laser beam is spatially scanned since only the laser focus point gives the transient absorption signals. We are now trying to apply this system to illegal drug detection.