bacteria blood care cell cells chemical chemicals disease drop exam graphic health healthcare hiv hospital illustration immunity laboratorium liquid medic medical microbe microbes microscope microscopic petri petri-dish test abstract abstraction background black blue colour colours cyan green microcosmos orange pink red texture white yellow bacterium blur bubbles hi-res lava light navy wallpaper water analyse backdrop blood analysis cleaning clusters concept contamination culture disinfect fungus germs health care illness immune immune system infection medicine sample science sickness slides swab tissue unclean virus color probiotics system blood cells hemoglobin iron