The light passing through lens cannot be directly focused inside biomedical tissues at depth deeper than 1 mm due to strong scattering, which fundamentally limits the use of imaging techniques such as confocal microscopy and two-photon microscopy, since these techniques demand confined light focusing inside tissues. To suppress the effect of light scattering in tissues and focus light deeper, the optical wavefront illuminating tissues should be modulated. To this end, three kinds of techniques are proposed: the wavefront shaping technique which uses the optical intensity in the wanted light-focused zone as the feedback; the time-reversed technique which combines acousto- optic modulation with optical phase conjugation aiming to focus light inside tissues; the technique of measuring transmission matrix of scattering media. These three techniques are reviewed and compared, while a technical prospect is given as for their biomedical applications.