Your personal statement should not exceed 3,000 characters (including spaces). The personal statement should describe your undergraduate experience, academic and professional plans, and reasons for wishing to participate in the program, include anything else you consider important for a judgment of your abilities (including articles, theses, books, other published materials, patented inventions, academic honors, prizes, etc.). PLEASE make sure to address this particular program- those addressed to other internships or discussing potential labs at other institutions will leave the admissions committee cold.