【如数家珍】〖rú sh ji zhn〗[as if enumerating one's family valuables -- can speak on a subject with great familiarity; be very familiar with one's subject]

如古涵今著诗典，

数往知来大同寰。

家传户诵全世界，

珍藏十袭子孙贤。

好像数自己家藏的珍宝那样清楚。比喻对所讲的事情十分熟悉。As clear as counting own treasures. Metaphor right talk about of thing very familiar. 同：了如指掌、了然入怀。反：一无所知。