High precision time-resolved spectro-photometry provides us with information about the cloud structure at different pressure levels of the atmospheres of brown dwarfs, and directly imaged exoplanet analogs. The monitoring of the easier observable exoplanet analogs, provide an idea on how exoplanet analog atmosphere structures look like. We show the results of spectrophotometric monitoring in the J-band of the Beta-Pic b exoplanet analog, 2MASS J2208136+2921213, during ~2.5 h using the MOSFIRE at the Keck 1 telescope. We find a maximum variability amplitude of 3% in the J-band, that decreases with wavelength, and slightly enhanced variability in the Na I alkali line. The Na I alkali line traces deeper layers of the atmosphere of 2MASS J2208136+2921213, allowing us to provide an estimation of where the different cloud layers are settled in the atmosphere of the object using radiate transfer models.