The ability to control particles in the quantum regime at the individual particle level has been a long sought goal in the
realm of quantum science for the past few decades. Such individually controlled entities could then serve as building
blocks for quantum simulators and computers. Of the many quantum objects developed in pursuit of this goal,
ultracold molecules, compared to their counterpart ultracold atoms, host rich internal states and unique inter-particle
interactions that could lend themselves useful in many applications. In this talk, I will discuss how we assemble single
molecules from single atoms trapped in optical tweezer arrays. This bottom-up approach utilizes laser cooling and
trapping techniques of ultracold atoms and has enabled us to achieve full quantum state control of individually
trapped molecules in an array. This opens up many exciting possibilities that can harness the rich properties of
ultracold molecules.