When massive stars exhaust their nuclear fuel they die in the most spectacular fasion - their central core collapses either to a superdense ball of only few kilometres in size, neutron stars, or to a black hole. The gravitational energy released during or soon after the collapse drives huge explosions known as Supernovae and Hypernovae. The life of neutron stars and black holes produced in this way remains most spectacular even after these explosions. Thanks to the angular momentum conservation they are usually rapidly rotating and the rotational energy can power strong outflows which then interact with the surrounding plasma leading to the phenomena like Pulsar Wind Nebulae. When a black hole/neutron star is a member of a binary system with a normal star as a companion it can accrete the matter being lost by the companion. Gravitational energy that is released during the accretion powers a variety of violent astrophysical phenomena. Some of it transforms into the rotational energy of the black hole/neutron star that keeps them spinning rapidly. Magnetic fields are likely to play a key role in driving the accretion as well as in powering and collimating the outflows from accreting systems. Given the relativistically strong gravitational field of the central object one would expect relativistically high speeds of the outflows and the observations do provide us with direct evidence for such speeds in the outflows from neutron stars as well as galactic and extragalactic black holes. Black holes created in galactic nuclei have a plentiful supply of matter from the dense interstellar medium and by accreting this matter they grow to an enormous size of up to billions of solar masses.