Water vapour will condense into droplets depending on the temperature. Clouds of all types require minute hygroscopic particles upon which water vapor can condense. When further cooled, the airborne water vapor will condense to form liquid water (dew). Vessels containing liquid nitrogen can condense oxygen from air. Oil vapors can also condense on more distant surfaces such as walls and ceilings. In turn this further caused the water vapor to condense and fall as rain. At this point the gas will condense at the same rate as the liquid evaporates. Some molecules are too small to condense. Less refractory products condense on surfaces of solidified particles. Although liquid nitrogen is non-flammable, it can condense oxygen directly from air. Both stations used cooling towers to condense steam. Orthophosphates can condense to form pyrophosphates. This effect occurs as giant molecular clouds condense out of the surrounding interstellar medium. There are no methane clouds as the temperatures are too high for it to condense. Without correct acetylation, DNA cannot condense into chromatin properly, which inevitably results in transcriptional errors.