This is the smallest butterfly I've made so far and it measures about 2.5" at the widest point x 1.5" high (6cm x 4cm).
The fabrics are a chambray shirting fabric and a cotton print from Amy Butler. It is fabric only--no interfacing.
It wasn't hard to make this size and if you want to make your own the fabric pieces for this one are 3" wide x 4" high (8cm x 10cm) and the blog post about making these butterflies can be found here.
The finished butterfly is being used to embellish this zipper pouch. The pouch was made using the no. 5 template in this document of pattern pieces (no sewing instructions).