Optical technologies have been increasingly utilized in biomedicine, including diagnosis, therapy, and surgery. In almost all of these applications, photons need to propagate some distance in tissue. Therefore, the capability of focusing or demodulating light information plays an essential role, largely determining the sensitivity and spatial resolution of these techniques. This has always been desired yet considered challenging within or through thick biological tissues due to the strong scattering of light. However, research has shown that the seemingly random scattering and the resultant speckle patterns are indeed deterministic within a certain temporal window.