This book contains different exciting structural phenomenon in weakly deformed nuclei (i.e the nuclei where the neutron or proton number close to shell closure). The detailed gamma ray spectroscopy technique which includes how to measure spin and parity of the exciting states as well as to measaure the lifetimes of these states with picoseconds order are described in this book. This book will be helpful for those who start their research carrier with gamma ray spectroscopy.