One-quarter of all American households now have an Amazon Echo powered by Alexa. But the surge in popularity of these virtual assistants comes with new questions about convenience, and privacy — especially as the company looks to make the smart speaker more "human."

Alexa has captured 70 percent of the voice market share in the United States, according to Alpine AI, with customers turning to the device for anything from playlists to recipes to finding their phone. It's become a major source of revenue for Amazon, in particular because it generates larger spending from Amazon Prime members, according to a new report by Consumer Intelligence Research Partners.

NBC News obtained exclusive access to Amazon’s Seattle headquarters and an interview with the executive in charge of Alexa, Toni Reid, to learn a little more about the future of this pint-sized device.

Reid has worked at Amazon for 20 years, first joining as a member of the then-startup’s recruiting team bringing new talent to the company.

“I started in recruiting and it was actually a really great place for me to be because I ended up learning a lot about different parts of the business,” Reid recalls about the early days of Amazon. “I moved from there into product management. One of the teams that I supported actually hired me into their business, and from there I just started taking on new and bigger opportunities.”

Inside Amazon’s “Day One” Building in Seattle lies an inconspicuous office door that leads to a smart-home lab, which Reid and her team use for testing and usability. The lab is designed to look like a modest-sized apartment — but with two kitchens. Amazon brings almost finished products to this space to better understand how customers use their Alexa device.

“It's all voice controlled,” Reid says of the apartment laboratory. “We want to know what customers are experiencing and how they are using our devices in a natural environment.”

Alexa has run into several privacy problems in recent months, including the device randomly laughing, and an incident in which an Echo reportedly recorded a husband and wife at home and sent that recording to a random contact.

When NBC News asked about these incidents, and whether customers can still trust Alexa despite these mishaps, Reid said, “Absolutely. And you know part of that is on us from an education perspective, so that customers understand the new technology… so that they understand when you say 'Alexa' it is only listening for the wake word and when it hears that wake word the device opens up and starts streaming.”

Reid says the ultimate goal for Alexa is to become more human-like. To achieve that, Amazon wants to make the device more personal. For example, she wants the Echo to be able to differentiate between voices in a home or office and tailor its responses to that individual’s preferences.

With that, though, comes serious questions about how adults and children build relationships with voice assistants powered by artificial intelligence.

When people tell Alexa “I’m depressed,” there are issues around responsibility from the device, said Amazon.

“A lot of people were having conversations with Alexa. Some of these things didn't need a response — like 'Alexa, I love you,' or 'Alexa I'm lonely, I'm sad, I'm happy,'” Reid said. “So we're really thoughtful about some of the responses we have. Sometimes you can be lighthearted and fun and other times you have to be thoughtful: If someone says ‘I'm depressed,’ how do you handle that? So, [with] each and every one of these kinds of new experiences or interactions, we do think about ‘what is our responsibility here?’”

“We're thoughtful about the product that we build and that the teams and the people that are building it actually look and represent those customers,” she told NBC News.