For each of the past 25 years, TIME editors have highlighted the most impactful new products and ideas in TIME's Best Inventions issue. The first, published under a cover featuring the protracted Bush v. Gore presidential vote count in December 2000, covered about 35 inventions, including some that feel a world away: the Ricoh RDC-i700 (a digital camera that could post photos to the internet), the first 3D ultrasound imaging for pregnant parents, and a bike with two pontoons that intrepid cyclists could ride on a lake. Others could just as easily be on the 2025 list. Medtronic's Activa Tremor Control Therapy was featured in the 2000 issue as one of the first forays into deep brain stimulation as a treatment for Parkinson's. This year's issue includes the same company's newly FDA-approved upgrade to the same technology, BrainSense, which continually adjusts to patients' unique tremors.

This year's list further confirms our focus on people. One of the dominant AI storylines of 2025 has been the competition over people. Investors have poured hundreds of millions into startups, reflecting the perceived value of founders, and leaders of Big Tech firms like Meta's Mark Zuckerberg have reportedly offered nine-figure deals to attract prized technologists. Those hires, accompanied by frenzied rumors, have turned the once obscure competition over AI researchers into something that better resembles professional sports free agency. The stakes for beating the competition are so high that leading researchers are courted like NBA All-Stars.

As we were finishing this year's TIME100 AI, I had two conversations, with two very different TIME100 AI honorees, that made clear the stakes of this technological transformation. Sundar Pichai, who joined Google in 2004 and became CEO of the world's fourth most valuable company nine years ago, told me that introducing the company's billions of users to artificial intelligence through Google's products amounts to "one of the biggest improvements we've done in 20 years." Speaking that same day, Meredith Whittaker, a former Google employee and critic of the company who, as the president of Signal, has become one of the world's most influential advocates for privacy, expressed alarm at the dangers posed by the fact that so much of the AI revolution depends on the infrastructure and decisions of only a handful of big players in tech. Our purpose in creating the TIME100 AI is to put leaders like Pichai and Whittaker in dialogue and to open up their views to TIME's readers. That is why we are excited to share with you the second edition of the TIME100 AI.

What is unique about AI is also what is most feared and celebrated--its ability to match some of our own skills, and then to go further, accomplishing what humans cannot. AI's capacity to model itself on human behavior has become its defining feature. Yet behind every advance in machine learning and large language models are, in fact, people--both the often obscured human labor that makes large language models safer to use, and the individuals who make critical decisions on when and how to best use this technology. Reporting on people and influence is what TIME does best. That led us to the TIME100 AI.

If you were hoping for one, definitive answer to this question, you may need to readjust your expectations. The truth is in the nuance. Every subscriber, and their relationship with your company, is unique. What's more is that every person behaves differently throughout their day. We all have different schedules, priorities, and distractions that often dictate when and where we check our email. If there was some magical time to send email, then your subscribers' (as well as your own) inbox would become flooded at that time every week. A better question to ask would be, "is there a best time for our company to send email given what we know about our subscribers?" Like all marketing channels, we must take specific steps to understand what works best for our audience. Some marketers prefer to use a test-driven approach for learning this, while others use buyer personas and qualitative feedback to optimize send time. There are even a few tools that use artificial intelligence to look at past email engagement, and customize future send time for you. Rather than try to discover individual best times, we asked marketers from the Databox Partner Program about the strategies they use to find the best time for any sales or marketing email. We grouped the responses by strategy so you can learn a range of ways to execute each one. Some of the participants even shared why they do not believe send time is a major factor, and instead focus on other parts of the email. Some tools can change the send time of each individual email based on past engagement history. Here's how this works- if you do not already have extensive email engagement data, the tool will send your emails at randomized times over the course of a few weeks to build a profile. Then, the tools will begin to personalize the send time based on past opens and clicks.