Figure 1: (a) Sketch of the pairing potential $\mathrm{\Delta }$ on both sides of a normal-superconductor interface [7]. $\mathrm{\Delta }(r)$ jumps abruptly at the interface, then recovers gradually to its bulk value over some length scale on either side of the interface. (b) Giant proximity effect is demonstrated in a superconductor/normal/superconductor sandwich junction at the measurement temperature $\text{T}=30\text{K}$ [8]. (c) Coupling an underdoped to an overdoped cuprate results in higher $T_c$ than would be found in either alone [11]. (d) Coupling a metallic cuprate to a superconducting cuprate results in a higher $T_c$ than has ever been found in this family of materials [12, 13]. In (b-d), all information comes from bulk transport or magnetic measurements; although $T_c$ can be determined accurately, no local information from the interface is available. (e) The geometry of the scanning tunneling microscopy experiment of Parker et al. allows nanoscale spatially resolved information from the vicinity of the metal-superconductor interface. In particular, Parker et al. show that regions of low pairing energy scale $\mathrm{\Delta }$ are likely to persist to higher $T_p$ if they are proximate to regions of higher pairing energy. The gap ($\mathrm{\Delta }$) colorbar is aligned with the pairing temperature ($T_p$) scale via the relationship $2\mathrm{\Delta }/k_B{T}_p=7.9\pm 0.5$ [14]. Black trace shows $T_p$ that would be expected for this simple local relationship; blue trace sketches the observed $T_p$. Note that $T_p$ is higher at point B than at point A, due to proximity to regions of larger $\mathrm{\Delta }$.