Fischer's scientific work was mostly concerned with the investigation of the pigments in blood, bile, and also chlorophyll in leaves, as well as with the chemistry of pyrrole from which these pigments are derived.
O traballo científico de Fischer estaba principalmente relacionado coa investigación dos pigmentos do sangue, a bile e tamén a clorofila das follas, así como a química das porfirinas, dos que derivan eses pigmentos.