Thaw a vial of stem cells, in tissue culture hood, by rubbing it between your hands. Pour it directly throughout a 25 cm^3 cell culture dish containing tissue culture media. Swirl the dish in a "figure 8" to optimize even distribution of cells.
View the cells the following day under a light microscope to ensure even distribution and expansion of cells. Cells will form circular colonies throughout the dish. Continue to examine the cells daily until they reach confluency (>70 percent coverage of dish).
Monitor stem cells daily to ensure that they don't begin to overgrow, as this can cause them to differentiate, and once that happens, they cannot return to their undifferentiated state -- entire lines of stem cells are wasted this way. The rate of growth of stem cells depends on the type of stem cell -- human stem cells might take 10 to 12 days to become adequately confluent, while certain types of animal stem cells may grow more quickly.
Split the cells, when they reach confluency, into 75 cm^3 dishes with 1 to 2*10^6 cells/dish. Change the media at least every three days.
Monitor the plated cells and passage (divide) them into more dishes before they reach confluency to ensure the long-term health of cells and avoid differentiation.