Origin, Current Status, and Future Perspectives of Chemical

Cells are the organizing units of life. However, not all cells are alike; individual cells can differ significantly from their neighbors. These differences can be due to genetic, environmental, cell cycle, or stochastic effects, and these differences can have profound effects upon the behavior of a cellular population. A knowledge of the function and composition of individual cells will lead to deeper understanding of the response to disease, development, and environmental insult. Most biological techniques are incapable of determining cellular heterogeneity. Instead, most biological techniques begin with the homogenization of many millions of cells, and those techniques simply report the average composition and response of the population. These methods are inherently blind to the distribution of the cellular population. There is a simple reason why most biological measurements are performed on millions of cells. Cells are small, and very few biological techniques are capable of analyzing the minute amount of material contained within a cell. Consider a typical cell from a higher eukaryote. That cell might be 15µm in diameter, corresponding to a volume of 1 pl and a mass of 1 ng. The cell is roughly 15% protein, corresponding to 150 pg; roughly 7 % nucleic acids, corresponding to 70 pg; and roughly 2.5 % carbohydrates and 2.5 % lipids, corresponding to 25 pg. Analysis of this minute amount of material is a formidable challenge