Virtually all life depends on the availability of light, including the light that powers photosynthesis (the process of synthesizing energy). Light travels in waves, and its energy is contained in packets called photons. The energy of a photon is inversely proportional to the wavelength of the light—the longer the wavelength, the less energy per photon. Sunlight consists of a spectrum of colors present in light, with each color represented in a specific wavelength along the electromagnetic spectrum. In general, the most effective wavelengths of light for photosynthesis are blue (at 430 nm, or nanometers, on the electromagnetic spectrum) and red (670 nm). Curiously, green plants have the hardest time with the photosynthetic process in green light.