Molecular Beam Epitaxy is a technique, which has been used to grow semiconductor thin film structures. In this process reactants fluxes are incident onto a substrate held at an elevated temperature. Typically the structure is grown by an appropriate shuttering sequence that is based on extensive pre-calibration. In this talk I am going to discuss the use of several sensors to monitor MBE in real-time. A discussion of the advantages and disadvantages of the various techniques will be given. The utilities of ellipsometry, desorption mass spectrometry, and atomic absorption for in-situ targeting of composition and growth rates will be given. As well as the advantage of integrating absorption band edge spectroscopy into substrate temperature control and its coupling to the various other sensors.