Nasal columella separates the nasal hole to the left and right. And it is the lower part of the nasal septum.
Columella from front and side (It looks natural when it slightly convex and looks about 2mm long from front)
But if columella is too long (hanging columellar), your nose may look too big, in other hand, if it is too retracted, your nose may look sagging.
Retracted columellar correction
Retracted columella can be corrected with cartilage grafting, and if ala is too low for columella, it can be improved with ala resection.
Hanging columellar correction
On the contrary, if columella is too protruding, resecting part of nasal cartilage or partially removing of nasal septum cartilage can be arranged. -> The correction of hanging columella
And last but not the least, columella correction is commonly done along with nasal tip surgery.
In many cases, nasal tip surgery requires support from columella, and nasal septum cartilage and ear cartilage is commonly used.
You can have an ideal nasal shape with careful design of columella length and shape.