The large Binocular Telescope is currently in the pre- erection phase. The instrument has been already funded and its first-light is expected shortly after that of the LBT. Given the peculiarity of the telescope optics we designed tow prime focus cameras with two five-lens refractive correctors, optimized in the blue-side and red-side of the visible spectrum respectively. This independent coating. Detectors also reflect this choice, being optimized separately. We present the most relevant features of the instrument, the optical design as well as the structural and mechanical layout. Each of the two Prime Focus cameras gather light form a very fast, F/1.14 parabolic primary mirror. The field is corrected over roughly half a degree in size, allowing optical performances in terms of 80 percent of Encircled Energy in better than approximately 0.3 inch. Focal length is slightly increased in order to provide a better sampling using 13.5 micrometers pixel size chips. The CCD array is made up with 4 EEV 42-90 chips, per channel, to obtain an equivalent 6000 by 6000 pixels optimizing the AR coating to the U,B,V and V,R,I,Z bands respectively. The array will be read out in 10 seconds using a 1Meegapixel/second controller with four video channels. The cryostat will use a state of the art dewar to reach an holding time of several days using a limited amount of liquid nitrogen. The whole mechanical design has bene modeled using Finite Elements analysis in order to check for mechanical flexures of the mount tube and of the optical components by themselves. A brief overview of the informative facilities to be provided with the instrument and of a few science case studies that can be attacked by this instrument are also given.