Lithium Web in astrophysics: insights and problems

Lithium (Li) is widely used as a test of the cosmological model, a probe of stellar structure, and an age indicator of young stellar clusters. It is the very element that presents deep insights, yet many problems to astrophysics.
I will discuss problems and puzzles that Li introduces in astrophysics, including cosmological Li problem (and a stellar solution to it), Li-rich giants problem (Galactic and extraGalactic), Li problem in the Sun, the Galactic Li evolution (in the thin and thick discs), and the interstellar Li content.