Isabelle Olsson, lead industrial designer for Google Glass, showed off a couple pieces of Google history as well as its near future today at Google I/O when she modeled two prototypes.

First, she showed off a huge, clunky early model typical of earlier prototypes of the device:

Google Glass early

“I will never forget the first day on the team,” she said. “I walked into a room full of people wearing these crazy things on their heads. … It’s kind of heavy. How do you go from something like this to what we’re all wearing today?”

Three guiding principles in making that gradual evolution, she said, were lightness, simplicity, and scalability.

“We are obsessed with weight” Olsson said. “We care about every single gram.”

She said they also strive to make Glass modular so it can be used in other cases, such as prescription Glass units, which she showed the audience:

Google Glass Rx