What is embryology? How does its study lead us to understand evolution?

An embryo is defined as an organism which is in the early phases of growth from zygote formed during fertilization to the start of third month of pregnancy. The branch of biology that studies the various phases of embryo growth is called embryology. The traits in embryos of pisces, amphibians, reptilians, aves and mammals are found to be similar and also look alike. Hence, embryology leads us to the understanding of evolution.