Agnolo Bronzino was a Florentine painter and poet who was widely known for his beautiful portraits (he painted many of them in Cosimo di Medici's court) and exquisite style. His models looked often cold and distant, as the young girl we see here. She is not very happy, is she? The prayer book, which she holds with a delicate hand, may be a reminder of a religious upbringing. I don't think she chose the subject herself - you can almost picture it: a small, indifferent girl thinking of the hours to come, hours of sitting, being dressed up in her finest clothes, a mother giving her a small prayer book, then they explain to her how to sit, how to hold the prayer book etc. And so, she is immortalized.