Abstract: Motility contrast imaging (MCI) is a depth-resolved holographic technique to extract cellular and subcellular motion inside tissue. The holographic basis of the measurement technique makes it highly susceptible to mechanical motion. The motility contrast application, in particular, preferably includes increased mechanical stability because the signal is based on time-varying changes caused by cellular motion, not to be confused with mechanical motion of the system. The use of the resulting spectrogram response signatures, or “fingerprint” data, of known compounds is disclosed to screen new compounds for leads as to those having potentially beneficial mechanisms of action. The “fingerprint” data of known toxic compounds can be used to screen new compounds for toxicity.