The main source of light
on Earth is the Sun.

Sunlight provides the energy
to create sugars
which release
energy into the living

virtually all the energy used by living things.

another important source of light
for humans has been fire,
from ancient campfires
to modern kerosene lamps.

With the development
of electric lights
and power systems,
electric lighting has all but replaced firelight.

Some species of animals generate their own light

fireflies use light to locate mates,

vampire squids use it to hide themselves from prey.