This is a tutorial for crocheting a baby jacket at the age of 3 to 6 months. This video shows the first part -- back part, next parts contain front parts.
Corresponding material recommendation: Wool http://www.amazon.com/gp/product/B00WQ9NBWW/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=B00WQ9NBWW&linkCode=as2&tag=wwwcrochetd0e-20&linkId=3SLHXMZC2N64HLXS