In this article, we review some of our tunneling results on various high-T_c cuprates (Bi₂Sr₂CaCu₂O_8+δ(Bi2212), Bi₂Sr_2-xLa_xCuO_6+δ, Tl₂Ba₂CuO_6+δ, (Cu,C)Ba₂Ca₃Cu₄O_y) including the doping dependence and temperature dependence of dynamical conductance. The conductances exhibit well-defined superconducting gaps as well as sharp dips and broad hump features, and for Bi2212 these are found over the entire doping range. The dip and hump features are observed in single-, double- and 4-layer materials, indicating that these are intrinsic properties of the Cu-O₂ plane in high-T_c cuprates. From the detailed examination of tunneling conductances as a function of doping and temperature, we find that the observed energy gaps at low temperature are of superconducting origin. In addition we find that the superconducting gaps and humps monotonically increase with decreasing doping despite of reduction of T_c in the underdoped regime, with both of them scale with the antiferromagnetic superexchange interaction J, such that Ω^hump  ~ 3Δ ~ 2J. Tunneling spectra in underdoped Bi2212 display a more pronounced hump feature suggestive of second gap in the density of states. It is observed that the hump feature in the tunneling conductance is consistent with other experimental observations of the so-called high-energy pseudogap, which may have magnetic origin. On the other hand, the temperature dependence of the conductance on underdoped Bi2212 by SIS break junction showed that the superconducting gap smoothly evolved into so-called low-energy pseudogap, whose characteristic temperature is T^*. The trend of superconducting gap is similar with that of low-energy pseudogap with the ratio 2Δ/kT*~6, indicating the low-energy pseudogap is due to some form of precursor of superconductivity. Concerning to dip structures observed at Ω^dip/e with respect to zero bias, we find that the dip strength is maximum at optimal doping and that the feature resembles the strong coupling effect due to a bosonic excitation. The mode energy, Ω =Ω^dip  - 2Δ for SIS junctions, scales as 4.9kT_c over the entire doping range. These features link the dip to the resonance spin excitation and suggest this excitation is important as glue for electron pairing.