We investigate the relativistic features of the tunneling ionization dynamics of highly-charged ions in super-strong laser fields. The quantum dynamics in the classically forbidden region is shown to feature two time scales, the typical time that characterizes the probability density‘s decay of the ionizing electron under the barrier (Keldysh time) and the time interval which the electron wave packet spends inside the barrier (Eisenbud-Wigner-Smith tunneling time) [1]. In the relativistic regime, an electron momentum shift as well as a spatial shift of the ionized electron wave packet along the laser propagation direction arises during the under-the-barrier motion. While the momentum shift is connected with the Keldysh time, the Eisenbud-Wigner-Smith time is imprinted on the wave-packet‘s spatial drift. The signature of the momentum shift is shown to be present in the ionization spectrum at the detector and, therefore, observable experimentally. In contrast, the signature of the Eisenbud-Wigner-Smith time delay disappears at far distances for pure tunneling dynamics. Spin effects arise during the relativistic tunneling ionization process [2]. We have investigated the spin-resolved ionization dynamics employing relativistic Coulomb corrected dressed strong field approximation (SFA) [3], and taking into account the laser field driven electron spin dynamics in the bound state. Even if an electron is very tightly bound to an ionic core, its spin dynamics may still be crucially affected by a laser field of moderate intensity, see figure. This effect is beyond the commonly accepted SFA and can be confirmed in a challenging experiment employing collisions of highly charged ions with ultra-strong laser beams. Figure: The qualitatively different behavior of spin in strong laser fields, within SFA (left) and the proposed theory (right). Spin effects in the tunneling regime of ionization are built up in three steps: spin precession in the bound state, during tunneling, and during the motion in continuum. Only the last two steps are included in SFA. The red, blue and green arrows indicate the initial spin, the spin after the tunneling, and the final spin, respectively. The spin quantization axis is along the laser propagation direction.