$p$-adic families of diagonal cycles

This note provides the construction of a three-variable family of cohomology classes arising from diagonal cycles on a triple product of towers of modular curves, and proves a reciprocity law relating it to the three variable triple-product $p$-adic $L$-function associated to a triple of Hida families by means of Perrin-Riou's $\Lambda$-adic regulator.