What makes a startup a startup? Is it the headcount of a nascent company that earns it the title, or the achievement of fast growth, driven either by a growing market or the mere fact founders have taken money from venture capitalists? Whatever your definition of startup, each organization is unique.

For our series, The First 100, we tracked down the first 100 employees at 100 startups and small businesses.

Joining a company with 60 employees may not be as daunting as joining a company with fewer than 10, but that doesn't mean you'll walk into a static atmosphere. As these early startup employees tell it, there are plenty of opportunities for personal growth — and quick promotions — if you're willing to bring some drive to the table. Below, we hear from employees 61 through 70 and growing companies like Airbnb, BlogHer, Rent the Runway and Vevo.

If you want more First 100 stories, check out the other articles in the series here.

61. Monique Maestas-Gower, BlogHer

Climbing the ladder... I entered the company as the office manager to get my foot in the door and become more familiar with the company. Through my various responsibilities, I became very interested in the events side of the business. As the event team grew, I was promoted into a sales planner role. This role gave me the opportunity to learn the ins and outs of events, especially sponsorship sales. I was also given responsibility to close some sales, and eventually I was promoted to focus fully on being a sales associate. Our events were growing, so our sponsor participation needed to grow as well. I oversaw the small and medium business group in order to expand this group’s presence at our events. My most recent promotion was to be an Account Executive selling our digital products. I already knew the BlogHer story and was excited to learn, and ultimately sell, a different product, and to transition over to the side of the business that drives the majority of BlogHer's growth and revenue.

Growth, growth, growth... My advice to anyone considering joining a company as a First 100 is to always know that with companies that are not quite startups but also are not large corporations, you may have to be willing and open to changing along with the company. Change is inevitable.

Today, BlogHer has 51 employees.

62. Michele Perry, Gazelle

First steps... I have always been drawn to early stage, small companies. I like being part of starting something big and growing a team and participating in a number of firsts for a company.

New beginnings... I dabbled with starting my own retail business just prior to joining Gazelle, but I realized I missed the camaraderie of being part of a team. Most of my career, I've worked for consumer internet businesses, including TripAdvisor, which is where I met our chief marketing officer, Sarah Welsh. She and I were part of the original marketing team that took TripAdvisor from an unknown brand to the largest travel site in the world. I was excited to partner with Sarah and the rest of the marketing team to create similar brand recognition for Gazelle.

Today, Gazelle has 130 employees.

63. Ian Logan, Airbnb

A rising tide... I started at Airbnb as a software engineer working along side the CTO, Nate Blecharczyk, on all things payments-related. All great things have small beginnings, and in addition to engineering I also responded to customer support tickets and handled manual processes to pay money to hosts. I quickly ramped up to independently design, build, and lead the company's payment platform. My role increasingly evolved to lead teams in growth, user acquisition and site performance while still being responsible for payments! New roles and responsibilities came about simply out of the need to push the business forward in addition to my growing hunger for achieving more.

Growing culture... Airbnb invests a lot in company culture and does its very best to keep the cultural bar high. Entrepreneurship is a big part of the culture, but so is being a host, which means having empathy for others, similar to the hosts in our community.

Today, Airbnb has more than 600 employees.

64. TaMeka Marshall, FrontPoint Security

The fast lane...I started off as a security consultant selling home security over the phones. Six months into the position I applied for and was promoted to training/QA analyst, a role in which I shared a 50/50 responsibility in assisting with the training of new hires as well as monitoring of recorded calls for quality assurance purposes. Three months into that role, I was promoted again to training supervisor, and my focus shifted mainly to sales training with little QA involvement. Finally, I was promoted to the position that I currently hold — manager of sales training, where I lead a team of training supervisors to complete FrontPoint’s world class training program. Overall, the new roles and responsibilities came about as the result of a lot of hard work and proving myself. That’s what I love about the company the most aside from the culture, they reward and recognize hard work and talent.

Icing on top... The culture is amazing and nothing shy of unbelievable. It is exactly why the friend that referred me loved waking up knowing that she was reporting to work at FrontPoint and why, I too, wake up happy and genuinely excited about the work day.

Today, FrontPoint Security has 380 employees.

65. Constantin Zhorov, Avigilon

Taking risks... Three years ago, I took a leap of faith moving to a new country and joining a new company that was still developing, hoping I’d land someplace where I would enjoy my work and my coworkers. The thing I love most about working at Avigilon is that I have the best of both worlds here: I get to work with products that are changing the industry and an amazing team.

Greater heights... Initially, my role as software developer was to implement designs composed by the senior software developers as part of a very small engineering group. During that time, the senior developers worked with me to explore the code and address increasingly complex projects. With time, I received more dynamic tasks that involved more autonomous design development. At the same time, Avigilon was experiencing rapid growth.

More firsts... Over the years, I have remained excited because I'm continuously involved in projects that solve problems no one had solved before.

Today, Avigilon has 500 employees.

66. Adria Barchi, Dos Toros

The best laid plans... I joined Dos Toros as a space filler between jobs. One of the guys I played soccer with at the time worked for Dos Toros and told me what a great company they were and how they like to promote from within so I took his advice and joined, mostly just thinking it would hold me over until I found something more suitable. I had been recruiting for financial IT, and it was not a personality fit for me at all. I was excited about something that I could do in the interim that would be fun and challenging. Little did I know how much I would end up loving it.

Anticipating the future... The company has evolved considerably since I have started. What started with a great idea, a concise menu, and a lot of warmth and loving customer service, has grown into a more organized and efficient place to work. The great part is that they have found a way to standardize us from store to store in processes without losing the ideals.

Room for growth... I started at the bottom as a crew member and worked my way up through shift leader, assistant manager, assistant general manager, and now I'm the general manager of one of our four locations. I have gone from just learning the ropes and being part of the team to running my own store and helping 30 different personalities find their own ways to constantly improve. My goal throughout my entire tenure has always been to make my boss' job easier.

Today, Dos Toros has 114 employees.

67. Jon Li, Vevo

Starting up... We run the SF office like a startup. Actually, the SF office didn't exist when I joined. It's rad, high-energy, and focused on building delightful products and collaborative teams.

The fast lane... I was hired to rebuild the desktop application. Three months later, my team launched the app at SXSW in 2012 to great reviews and huge impact on our user registration and view KPIs.

Growing lean... Being a young company challenges us to be smart about choices and clever about resourcing projects. We must constantly ask ourselves, how do we move fast while being understaffed? Are we making the best decisions? Our product department is fluid — we adapt to situations.

Answering the "why"... Music is the number one form of entertainment. I'm smack dab in the middle of it. I am doing something that 85% of the population wants. Music is human culture. It's life. I continue to apply learnings from the ecommerce background and attempt to apply it to the music industry. There's so much still to do.

Today, Vevo has 250 employees.

68. Katie Ellis, Rent the Runway

Office space... When I started at Rent the Runway, we were still fulfilling all of our orders out of our office in Soho, and were quickly growing out of that space. My second month at RTR, we all pitched in to pack up and move our operations to a much larger warehouse in New Jersey. I'll never forget that Friday night where everyone — including Jenn and Jenny — pitched in to make the move a success. Getting hands-on experience and learning how other parts of the business work was invaluable to me. It’s those late nights where you really get to know your team members and understand the value of your work.

From user to doer... I had been following Rent the Runway since its inception in 2009: I was on the wait list to join and subsequently an early adopter. I thought it was such a brilliant concept, and loved the story of how Jenn and Jenny started the business. If there was ever a picture of courage, conviction and confidence, they were it. They were the exact type of people I wanted to surround myself with at the impressionable age of 23.

Evolving roles... I started as a community manager, focusing on growing our social channels and creating programs to engage our members. It was an exciting challenge to be the mouthpiece for the brand, and even more exciting to interact with our customers on a daily basis. A few months in, I took on email marketing in addition to community management and worked closely with the design and merchandising teams to develop editorial calendars and create content. I wore many different hats and strengthened my ability to be agile, scrappy, and resourceful. It wasn't scary to take on new responsibilities, because I knew I had the support of the rest of the team, and it was okay to make mistakes and learn.

Today, Rent the Runway has 250 employees.

69. Julien Geffriaud, Zoosk

How to excel... What gets me up in the morning is a combination of the people, the awesome service we are providing to our customers, and the excitement of refreshing my pivot tables!

The bottom line... After four years at Microsoft, I was excited to have a bigger impact on the bottom line and get the opportunity to wear multiple hats. And that is exactly what happened. In my role at Zoosk, I know exactly how much I contribute to the company’s success on a daily basis, and I have been exposed to a lot of different topics, that I would never have had a chance to touch on in a big organization.

Setting the stage... In terms of size, the company has nearly tripled. It's been fun to see Zoosk go from a Facebook app to a multiplatform dating brand in 80 countries. I now feel like a veteran!

Today, Zoosk has 179 employees.

70. Tanya Singer, Retrofit

Level up... I heard about Retrofit when CEO Jeff Hyman first launched the company in 2010 and followed its progress. Two years later, Retrofit had a proven model and I was thrilled to be offered the opportunity to take it to the next level.

Running start... The first few weeks at Retrofit were the most dynamic start I've ever experienced! I took on a new role as vice president of engagement, working with our growing corps of businesses looking to help their employees lose weight and keep it off. After just a few weeks into that role, I stepped into leading the marketing department to introduce our new Retrofit Group product to the market, and was just named chief marketing officer last week.

Pervasive culture... Retrofit employees are all-in with whatever we do. The company culture is intense and mission-driven. We are all laser-focused on helping our weight loss clients succeed. We try to walk the talk, which means living an active, healthy lifestyle. As far as the product itself goes, I have never seen such clean software. The product experience is simple and sophisticated.

Today, Retrofit has 53 employees.