Blood is an essential component of human body. The picture illustrates a microscopic view of a colony consisting of red blood progenitor cells. These cells were isolated from bone marrow of an acute myeloid leukemia patient and cultured in vitro, meaning grown in laboratory, to identify potential of individual cells to grow into colonies or to differentiate. In this picture, light refraction through media gives an impression of space with the colony of cells resembling a little star.