hi siti i strongly recommend u Baby Signing Times by Rachel Coleman if u r serious about teaching ur baby sign language. I let my baby watch BST whn she was 7 mths, we also sign to each other. She first signed back at 9 mths, by one year old she knws 50 signs. She speaks in sentence of 3 words at 18 mths. Signing with baby highly recommended and if there's one signing product i would choose, that will be BST ! Enjoy!!