We observe water vapor condensing into liquid droplets on a daily basis, be it as dew drops on leaves or as droplets on the lid of a cooking pot. Since the work of Dutch physicist J.D. van der Waals in the 19th century, condensation has been understood to result from attractive forces between the molecules of a fluid.
Click here for original story, Self-propelled particles can condense by turning and moving toward crowded areas
Source: Phys.org