OTELO, (OSIRIS Tunable Emission Line Object Survey), will survey emission line objects using OSIRIS tunable filters in selected atmospheric windows relatively free of sky emission lines. Different high latitude and low extinction sky regions with enough angular separations will be observed yielding a total area of 1-2 square degrees. A 5 σ depth of 8×10^-18 erg/cm2/s will allow detecting objects of EW ~ 6, making OTELO the deepest emission line survey to date. OTELO is a deep space probe that will provide a representative sample of the Universe from z =0.24 through 6.7. Given the observing procedure, OTELO will allow studying clearly defined volumes of Universe at a known flux limit. In this contribution, a review of the project status is presented, together with some of the most significant evolutionary studies that will be tackled.