Or they sign a licensing agreement. A wide variety of designs have been marketed since the first CFL in 1981. A few can be seen here and in these ads. In the unlighted tube, tiny drops of mercury appear as silver specks. In the lighted tube an electric current has heated a gas that in turn has vaporized the mercury.
Fluorescent tubes make white light in two stages.
Very little energy is lost in either of these stages. That is why fluorescent lamps are so efficient. Each phosphor radiates a different color light and these colors can be combined to create white light. A fluorescent lamp emits white light because it has a carefully formulated mixture of phosphors on the inside of the tube.