  Harmonic lasing provides an opportunity to extend the photon energy range of
existing and planned X-ray FEL user facilities. Contrary to nonlinear harmonic
generation, harmonic lasing can generate a much more intense, stable, and
narrow-band FEL beam. Another interesting application is Harmonic Lasing
Self-Seeding (HLSS) that allows to improve the longitudinal coherence and
spectral power of a Self-Amplified Spontaneous Emission (SASE) FEL. This
concept was tested at FLASH in the range of 4.5 - 15 nm and at PAL XFEL at 1
nm. In this paper we present recent results from the European XFEL where we
successfully demonstrated harmonic lasing at 5.9 Angstrom and 2.8 Angstrom. In
the latter case we obtained both 3rd and 5th harmonic lasing and, for the first
time, operated a harmonic lasing cascade (5th-3rd-1st harmonics of the
undulator). These results pave the way for reaching very high photon energies,
up to 100 keV.
