[He looks up when Hiro pokes in, and he smiles warmly as he turns his chair around to wave him over.]

Quite a number of things. You know how we inventors are, thinking of one thing and then another. But before that...

[He pulls out a small stack of papers and slides them across his desk towards Hiro.]

Thought you might want to look at those, see if they spark your interest.

[And when Hiro looks, he'll find them to be various plans and writings Tadashi had worked on while here.]