"Manipura is considered the center of dynamism, energy, will power (Iccha (pronounced ik-chh-a) shakti), and achievement, which radiates prana throughout the entire human body. It is associated with the power of fire and digestion, as well as with the sense of sight and the action of movement. Through meditating on Manipura, one is said to attain the power to save, change or destroy the world." - Taken from Wikipedia on the Manipura chakra.
This center is a ganglia of nerves that sits around in between the kidneys. It's how you create your bodies power and energy. The Vedic call it a chakra or wheel of spinning light, said to make prana, the life force. It vaguely relates to the Chinese acupoint mingmen referred poetically as "the door of life". Anxiety can be tamed here as adrenaline's roots reside within the adrenals which sit upon the kidneys. Stress also can be eased with this point. It grants power and radiance of the sun to those who cultivate it. Those do be warned not to overuse or foolishly use the power created as it can inflate your ego and inner darkness. Hence moderation is advised.
Anatomy Anatomically our chest muscles and the upper back(teres major/minor) can be seen as one section of the body, if a circle be applied around it from a birds eye view/horizontally laid. Under this is the rib cage area where our upper abs, serratus and the lats reside around the back area. This is the upper abdominal region while the lower region spreads down to the lower belly. Our kidneys reside around the lower rib region. So if you were to feel the rib cage and see where it dips into the lowest point around the naval level horizontally, this is somewhat where the kidneys reside. They're still a little bit inside the ribs though. I recommend looking up some images and feeling in your body. They feel like two fist sized dense masses with a hollowish spiritual space within the middle of them(Not inside the kidneys but the space in between them). This spiritual space is our cultivation center - Solar Plexus.
General knowledge
Dark under eyes are a sign of kidney, liver or stomach issues usually. Cultivation of this center can help to clear them up,
Weak personal power, feeling of helplessness, depression, chronic fatigue, anxiety. weak personality, a lack of self centeredness are all negative attributes related to a weak solar plexus center. Similarly overly strong ego, overbearing personalities, excessive energy conditions can be related to an excessively active center.
Kings were known partly for this center, the gold color usually represented this along with white for the higher mind and red for the root.
Musical ability is actually related to this area too. The roman god of the sun had a relation to the lyre. Soul musicians use this center heavily to get that honey like, bright and giant vocal energy.
Exercises and meditations
A basic movement exercise is to center your focus around the solar plexus and roll it around, co-incidentally it is a major movement joint where the rib cage moves from the belly area. Move your spine and abdominal left, forward, right, back, in a circular motion and then the opposite direction.
This is just a simple exercise to clear physical blockages and get you to feel the warmth.
Next is the main meditation.
Start by sitting in whatever position is comfortable for you. Take a moment or two to clear yourself of thoughts, feelings and other disturbances. Once ready locate the abdominal center - solar plexus. It should feel like a bright, warm, clear area in between your lower ribs. Continue breathing and holding focus into this space, not overly pressuring it but feeling it with diligent focus,
Slowly it may grow stronger and other areas around it may open up, warm up and gain new circulation.
After around 10-20 minutes or when you've grown tired of this meditation you may stop.
Make sure to allow your natural focus and energy to spread throughout the body after finishing as it's not good to hold focus in a single area or center while performing daily tasks as the body gets starved of energy and becomes cold.
Ending notes
Cultivate this center well as it will give you the energy to perform whatever it is you wish without the use of stimulants or other aids.
*Disclaimer* This is not medical advice. I am not a medical practitioner.