Although most reptiles lay eggs, some reptiles retain the eggs, and the young are hatched inside the mother's body. Others are completely live-bearing, and no hatching is involved at all.
One famous group of reptiles that never lay eggs is the viper. These venomous snakes are completely ovoviviparous, meaning that the eggs are retained. Related snake groups, such as cobras, do not retain their eggs, but they do exhibit egg-guarding behavior in contrast to other reptiles like sea turtles that lay their eggs and offer no protection to them afterward.
Other examples of ovoviviparous snakes include the garter snakes and boas. Lizards that bear live young include the common horned lizard, the common European lizard, some species of iguana, skink, gecko and Jackson's chameleon.