It was starting from the word "Australia" on my sweater and since then he likes to know more letters. At this moment, he knew well the letter A, U, I and O. Amazing isn't it and he is not even 24 months yet. Now, he likes to say it every letters that he saw it.
I bought these alphabet via Ebay, they are cute isn't it. Matthew LOVE it. It is a magnetic and I put it on our refrigerator. Together with Jason or me, we "teach" Matthew in fun way to know more letters. Jason is a great "teacher" for him :D