The fourth chakra is the heart chakra, located at the heart.
Color: green
Sound: yam
Types of food: vegetables and greens
Aromas: rose, amber, lavender, jasmine, marjoram
Best therapies: give, love, donate, share
The heart chakra is associated with the element of air, and therefore with fluid breathing and pranayama (breathing practices.)
The heart chakra is associated with love, compassion, and forgiveness.
If the energy here is deficient, the chest might appear collapsed, with the shoulders rounded forward. If might feel difficult to breath, as though there is a heaviness in the heart/chest.
If the energy here is excessive, one might give of oneself too freely, without adequate self-care. It might present as codependency.
Another source: thegroundingtouch.com