Once finished with the immigration doctor and having sent all the paperwork to the USCIS (U.S. Citizenship and Immigration Services) you will start receiving receipt-letters, one per sent document. Among those receipt-letters you will receive an appointment letter informing you of where and when to take your biometrics.
What is the Biometrics appointment about? is the part of the process in which they ask for and collect your unique physical recordable data and your picture, among other things. Do you remember when you entered the country and the passport control took a picture of you and your fingerprints? The biometrics is similar, but a bit more intense. They will take your fingerprints of each individual finger and of groups of fingers at a time.
However, before they take your biometrics they make sure that you have all the documents needed for the appointment. In other words, the appointment letter with your appointment information, an Identification Document (ID), and in case you are changing your last name, the marriage certificate.
Then they ask you to fill in a paper with questions about your physical attributes: weight, height, hair color, eye color, etc. So make sure you know all that before you go!
NOTE to all people involved in the process: if you cannot make it to the appointment, make sure you follow the instructions on the letter to change it (but hurry up, because the later you request the change, the longer the whole process will be). Be aware that if you do not show up it will considered that you abandon the process... you do not want that.
My experience with this part of the process was quite positive. The place where I had the appointment was about 2 hours away by car, and fearing being late we arrived 1 hour before the appointment time. That was not a problem, they checked my documents, gave me a waiting number and asked me to fill in a paper in the meanwhile. I waited 2 turns and there I was, putting all my fingers, one after the other, in the little screen. After that they took a picture (for what I was not prepared) and they made me take the glasses off. It turned out that they used this picture for the Green Card itself, so make sure you are looking good!
And done! In 30 minutes I was back in the car and on my way home happy as can be with my accomplishment for the day. Now what is left to do is wait for another letter that will inform me of what step comes next.
