瞭若指掌

To understand clearly; to be clear-sighted; to watch from a distance; eyes bright.

If; supposing; as if; like; to seem; to resemble; to be compared to; a type of fragrant herb; to obey; surname Ruo.

Finger or toe; to point at or indicate; to refer to; to count on or depend on; a unit of width.

Palm of the hand; sole of the foot; paw; to hold or wield something; to manage or control; to slap with the palm.