Morphology is destiny for what a robot can touch. Two link lengths define an annular workspace: nothing closer than their difference, nothing farther than their sum. Inside that ring, the joint angles that place the hand come from a short piece of trigonometry, the inverse kinematics. This is why hand and arm design is a spec sheet, not an afterthought: the 2026 humanoids advertise their reach as degrees of freedom, from the Unitree G1's 23 rising to 43, to a 22-degree-of-freedom Optimus hand. More joints buy dexterity and the ability to reach around obstacles, at the cost of mass and control complexity.