The promise of jobs and prosperity, among other factors, pulls people to cities. Half of the global population already lives in cities, and by 2050 two-thirds of the world's people are expected to live in urban areas. But in cities two of the most pressing problems facing the world today also come together: poverty and environmental degradation.
scientists can test differences of the area with pigmentation by observing which is lighter and which is darker however they use microscope to look the difference of the pigmentation over the cells.
