This issue explores the unique value proposition that engineers and engineering disciplines present in addressing the National Academies’ Grand Challenges. Covering topics ranging from the global sustainability challenge to the sequestration of carbon to transformations in our water management system, the articles in this issue show how engineers are vital to creating a world in which humanity can thrive.

• A Word from the NAE Chair Intelligent Systems Engineering?
• Editor's Note: Welcoming Changes
• Issue Editors' Note Engineers Matter - But Why?

The world’s cities face increasing threats from natural disasters, aging infrastructure, traffic, and resource constraints. The articles in this issue examine smart infrastructure, sustainability, net zero carbon options, and autonomous driving, among other approaches to smart and sustainable cities.

• A Word from the NAE Chair: Infrastructure Here and Abroad
• Guest Editor's Note: Engineering for Sustainable Smart Cities
• A Metastructure Approach to Smart and Sustainable Cities

The covid-19 pandemic suddenly directed awareness to potential health impacts of the built environment of everyday living – schools, dwellings, offices, public buildings, and other spaces. This issue explores the “microbiome” of the built environment in the postpandemic reality in terms of ventilation performance, filtration, understanding and quantification of transmission risk, protection of “benign” microbes, and the important role of equity, among others.

• A Word from the NAE Chair: Engineering Leadership
• Editor's Note: Thoughts on the Future of the Building Microbiome
• Issue Editors' Note: Microbial Challenges in the Built Environment