<unk> s are evolved from main sequence stars with masses in the range from about 0.5 solar masses to somewhere between 4 and 6 solar masses .<unk> s are stars with radii tens to hundreds of times larger than that of the Sun which have exhausted the supply of hydrogen in their cores and switched to fusing hydrogen in a shell outside the core. Since the inert helium core has no source of energy of its own, it contracts and heats up, and its gravity compresses the hydrogen in the layer immediately above it, thus causing it to fuse faster.  This in turn causes the star to become more luminous (from 1,000 to 10,000 times brighter) and expand; the degree of expansion outstrips the increase in luminosity, thus causing the effective temperature to decrease. In stars massive enough to ignite helium fusion, an analogous process occurs when central helium is exhausted and the star switches to fusing helium in a shell, although with the additional complication that in many cases hydrogen fusion will continue in a shell at lesser depth — this puts stars onto the asymptotic<unk>  branch.  The decrease in surface temperature shifts the star's visible light output towards the<unk>  — hence<unk> , even though the color usually is orange. Main sequence stars of spectral types A through K are believed to become<unk> s. 
Very low mass stars are thought to be fully convective and thus may not accumulate an inert core of helium, and thus may exhaust all of their fuel without ever becoming<unk> s.  Such stars are commonly referred to as<unk>  dwarfs.  The predicted lifespan of these stars is much larger than the current age of the universe, and hence there are no actual observations of these stars aging.
Very high mass stars instead develop to supergiant stars that wander back and forth horizontally over the HR diagram, at the right end constituting<unk>  supergiants. These usually end their life as type II supernovae.
If the star is heavier than 0.4 but less than 2.57 solar masses, the addition of helium to the core by shell hydrogen fusing will cause a helium flash — a rapid burst of helium fusing in the core, after which the star will commence a brief period of helium fusing before beginning another ascent of the<unk>  branch. Stars more massive than 2.5 solar masses, but less than about 4 to 6, enter the helium fusing phase of their lives much more smoothly.  The core helium fusing phase of a star's life is called the horizontal branch in metal-poor stars, so named because these stars lie on a nearly horizontal line in the Hertzsprung-Russell diagram of many star clusters.  Metal-rich helium-fusing stars do not lie on a horizontal branch, but instead lie in a clump (the<unk>  clump) in the Hertzsprung-Russell diagram.
Actually, such stars are not big<unk>  spheres with sharp limbs (when one is close to it) as displayed on many images. Due to the very low density such stars may not have a sharp photosphere but a star body which gradually transfers into a 'corona'.
Red giant
Clear cell
Large cell
Demegestone
Half and half nails
Eosinophilic
Corns & calluses
Fair coin