autumn backdrop background calm cirrus cloud clouds cloudy cosmos cumulus dreamy ecological ecology fluffy formation formations heaven heavens horizon light meteorology mood natural nature nimbus outdoor panorama peace peaceful rain skies sky space spring storm strato-cumulus stratus summer sunlight sunlit sunny texture tranquil tranquility wallpaper weather weirdvis winter analyse bacteria blood blood analysis cells cleaning clusters color colour concept contamination culture disease disinfect Ebola germs graphic health health care illness immune immune system immunity infection medical medicine microbes microscopic mitosis pathogens petri dish probiotics red sample science sickness slides swab test tissue unclean virus abandoned aging agricultural appearances brown colors colours corroded corrosion damage damaged dark decay derelict deteriorating deterioration Dirt dirty discarded discoloration discolouration disrepair dumped equipment exposed farm farming iron lines machinery machines metal neglect neglected old orange rough rust rusty surface surfaces textures unwanted variety wearing weathered weathering cogwheels frozen gears rusted teeth turning