either of two large organs lying within the chest cavity on either side of the heart; they supply the blood with oxygen inhaled from the outside air and dispose of waste carbon dioxide in the exhaled air, as a part of the process known as respiration.
Most babies first pull themselves up to a standing position between about eight months and 10 months. At this stage your baby will need to hang on to you or a solid piece of furniture. By 11 months she may be able to stand on her own.
Infant development: Milestones from 7 to 9 months. Your baby might surprise you with how quickly he or she is picking up new skills. Infant development milestones for a 7- to 9-month-old include sitting, standing and laughing. As your baby becomes more mobile and inquisitive, infant development takes off.