HEK 293 cells are widely used for transfection because of their high transfection efficiency and robust growth characteristics. The HEK 293 cell line was derived from human embryonic kidney cells and has been engineered to express the adenoviral E1A and E1B genes, making it highly permissive for the introduction of foreign DNA. This results in a high rate of successful transfection compared to other cell lines, making it a commonly used cell line for the study of gene expression, protein production, and other cellular processes. Additionally, HEK 293 cells grow quickly and are easy to maintain in the laboratory, making them a convenient choice for many researchers. Overall, the combination of high transfection efficiency, fast growth rate, and ease of maintenance make HEK 293 cells a popular choice for transfection experiments.