Nuclear fusion is the energy source of the Sun and all other stars. Time is coming when nuclear fusion will produce electricity. A five-part series Mastery of sun describes the state of the art of developing a fusion power plant. The fourth article deals with the nuclear components load and design of the power reactor blanket. Thermonuclear plasma is highly stochastic system characterized by a series of confinement failures. The most serious plasma disturbances include the edge localized mode instabilities ELM, vertical displacement events, disruptions and runaway electrons. The following plasma-wall interaction puts high demands on plasma facing materials of the first wall and divertor. The important component of the fusion power reactor also is the reactor blanket, ensuring the removal of energy from the reactor and the production of tritium. There are many design proposals of the blanket, some variants of them will be tested in ITER.