My daughter and I run a business together. She's my boss and mentor, and it's wonderful working with her.

• Liz (46) and Rich Muller (81) have built three successful companies together as daughter and father.
• Liz is her dad's boss and said it's important to be clear on roles and lead with respect.
• Rich said Liz's business sense helped him realize the value of his invention for their company.

This as-told-to essay is based on conversations with Liz Muller, a 46-year-old cofounder and CEO in Berkeley, California, and her father, Rich Muller, an 81-year-old inventor and CTO. The father-and-daughter duo has launched many companies together.

Three successful businesses they've created include: Berkeley Earth, a nonprofit that provides critical climate-science data; Deep Isolation, a nuclear waste disposal company; and Deep Fission, a nuclear energy company burying small modular reactors a mile underground.

They shared their experience working and living together as a family. The following has been edited for length and clarity.

Liz: Before working together, I'd been living in France for about eight years, working as an administrator at the Organisation for Economic Co-operation and Development (OECD). Part of the reason I returned to the US was the realization that I was an entrepreneur and wanted to start my own business.

I couldn't imagine a better person to start a company with than my father, Rich. He'd spent years in the energy and nuclear space and had all the right expertise.

Rich:. She would be my boss, and I would offer technical information.

Liz: We started a couple of initial companies that didn't take off. Now, we both work at Deep Fission, our third successful business — he's the CTO and I'm the CEO.

It's helpful that we have different areas of focus

Liz: I have business experience, and Rich is a fantastic inventor — that's one of his biggest strengths. Even better than that, he can invent on demand, which is a rare ability.

Rich: It's been wonderful working together. I felt blessed from the beginning. I bragged to everybody that my daughter was my boss. Here's something you'll rarely hear: she was my mentor, which was wondrous.

I'm enormously impressed with her capabilities. Once I asked, "Where did you learn all this from?" She said, "From you, daddy," a name she calls me at home, as we decided she would call me by my first name during work.

Working together as father and daughter isn't always easy, but it's meaningful

Liz: I'm a co-inventor on several of our patents, but he's the technical motor. I really enjoy our strategy sessions. They're essentially a free-form talk about anything and everything under the sun.

We've come up with our best inventions in these sessions, but halfway through, we might talk about what my kids did the other day. It's not 100% business, making it richer, and giving our brains exploration time, making our minds open to out-of-the-box ideas.

Occasionally, we may disagree, but family is most important, and he respects my judgment.

Rich: Working with your adult child is one of the greatest joys you can have as a parent.

My advice? Let them lead. Your child is no longer your student. They're your partner. That means respecting their judgment, letting go of the need to be right, and knowing when to step back so they can shine.

Liz: People often ask what it's like to build a company with my dad. The truth is—it's not always easy. The hardest part is when you're going through a difficult period or the company is crossing significant milestones. But it's one of the most meaningful and rewarding parts of my career.

The best advice I can give is this: Be clear on roles, and lead with respect. We stay in our lanes, challenge each other when it matters, and always assume good intent.

Living together as father and daughter is convenient

Rich: We all live together in this big, beautiful, brown shingle house that used to be apartments. My wife and I moved in originally as tenants and eventually bought it.

It's four floors, and my wife's an architect, so she redesigned floors three and four for Liz, her husband, and our two grandchildren, who are 11 and 15. We live in separate apartments, but I see them every day.

Interactions with Liz are very convenient, and it works out really well. During COVID, we were able to spend a lot of time tutoring our grandchildren, which was a blessing.

Liz: Rich makes coffee for me every morning, which is lovely. My kids will always say hi to him on their way out, and we have dinner together on Sundays.

Despite living in the same building, our biggest challenge is finding time to spend together. We're both so busy with work and other obligations that it's hard to carve out quality one-on-one time.

Nevertheless, we prioritize it and try to do it at least once a week. I'm sure other household members may find it annoying how quickly we can turn a family conversation toward work, but we try to be mindful not to do that too often.

We have a complementary working relationship, and we're proud of that

Liz: Our working dynamic sparked the idea for Deep Fission. Rich was exploring a question that a Deep Isolation customer raised: What would happen if we put fresh fuel, instead of spent fuel, deep in a borehole? Analysing this led to Rich's invention of the Deep Borehole Reactor.

Rich: But it was Liz who recognized the importance of the concept and fleshed out many of the details. Liz's mastery of the technology is very high. She recognized that we could potentially lower the cost of nuclear power by 80% by not needing the vast majority of the construction.

This was an example of the importance of our complementary skill sets — I had the idea, but Liz's business sense helped us recognize the value of the invention. It was an active back-and-forth, and we are co-inventors on the original patent.

Liz: We're both incredibly proud of how much progress we've made with Deep Isolation and Deep Fission. The industry response has been amazing.

People light up when they realize what we're building and the impact it could have on the future of nuclear. We're excited for what's ahead and grateful to be building it together as a strong, complementary team.

Our secret to success is simple: we're equals

Liz: The secret to our success is that Rich and I have complementary rather than overlapping skill sets. Many parent-child companies have a mentor mentality, where the parent teaches the child until the child is ready to take over the business, and then the parent retires.

We have always worked together as equals, with each of us bringing different areas of expertise.

Rich has no intention of slowing down. This work is his life's passion, and he's energized by the science. Of course, if things change, we'll make thoughtful transitions. However, right now, he's as sharp and engaged as ever, and we continue to think through new inventions every week.

If you work in a business with a family member and have a unique story that you would like to share, please email the editor, Manseen Logan, at mlogan@businessinsider.com.