Kekkei Genkai

A Kekkei Genkai is a bloodline trait passed down within a clan throughout generations. For example, the Sharingan is a Kekkei Genkai, as its been a dojutsu passed down throughout the Uchiha clan for generations. 
The first Kekkei Genkai seen in Naruto was Neji Hyuga's, giving him a strong dojutsu known as the Byakugan. The second was Kiminaro's, a strange but strong Kekkei Genkai that allots him the ability to sprout, grow, or even pull bones from anywhere in his body.