In astronomy, the first spectrographs used photographic paper as the detector. The star spectral classification and discovery of the main sequence, Hubble's law and the Hubble sequence were all made using photographic paper. The plant pigment phytochrome was discovered using a spectrograph that used living plants as the detector. New spectrographs use electronic detectors, such as CCDs which can be used for both visible and UV light. The type of detector depends on the wavelengths of light to be recorded.