Excerpted from:

http://meditationformultitaskers.blogspot.com/2012/06/muladhara-chakra.html

The muladhara chakra is the first of the upper chakras in the torso. Located at the base of the spine, this energy center governs memory and timing. As the center closest to the earth (represented by the color yellow), it plays an important role in keeping the asana stable and secure during meditation. The seed sound for this chakra is lam. Lord Ganesha is traditionally seated in this energy center, since he plays an important role in all beginnings. This "beginning" chakra opens the way for the other chakras, so it is a good idea to set things right in the muladhara before continuing with meditation. An easy way to meditate on the muladhara is to feel gravity pulling you down towards the earth as you sit.