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.
By 11 months your baby will probably be able to stand without support, stoop, and squat. By 12 months he may walk while gripping your hand, though he may not take his first steps alone for a little while longer (Harding 2014, Sheridan 2008) .ost babies take their first steps by their first birthday. By the time they're 15 months old, most toddlers are walking unaided, though often with uneven steps (Harding 2014, Sheridan 2008) . Try not to worry if your baby takes a little longer.