Holography is an optical technique enabling to record phase objects. Holographic interferometry uses this faculty to make a phase object interfere with a memory of itself at a preceding time, recorded on a hologram. Interference fringes therefore inform on any variation of the phase of the object. For the study of liquids, these phase changes can result from the evolution of temperature or concentration (via the index of refraction). This access to the real-time evolution of concentration can be used to measure diffusion coefficients, Soret coefficients or dissolution coefficients. Temperature fringes can be used to study convective flows.