Photosynthetic organisms use sunlight to provide the energy necessary to combine carbon dioxide and water to form organic molecules and ATP. Those same photosynthetic organism also use cellular respiration to breakdown those organic molecules whenever there is an energy demand greater than what can be provided by photosynthesis or in the absence of light.
In the year 1850, Rudolf Virchow was studying cells under a microscope, when he observed that cells were dividing and forming new cells. Realizing what he had observed, he understood that living cells reproduce new cells through division. Basing on his conclusion and realization, Virchow proposed that living cells came only from the other living cells.
They did it to get more detailed pictures of space
