From mattresses to razors, e-commerce has made an impact on just about every industry imaginable. Yet some markets have managed to fly below the radar of the e-commerce boom. Until now.

After identifying untapped profit potential, startups and giant corporations alike are investing in e-commerce in unexpected ways.

Case in point? These four industries were once thought to be un-disruptable from an e-commerce perspective. Yet e-commerce has come for them--and is completely reshaping these market landscapes in the process. Here's how.

1) The music industry.

It's no surprise that digital tech has changed the music industry. (Anyone who grew up in an era when bookstores reserved huge swaths of shelving for retail CDs can attest to that.) These days, people are more likely to listen to music via online streaming services or MP3 downloads than they are to purchase a CD.

But digital disruption of the $60 billion global music industry doesn't stop there. More recently, e-commerce has come for the music market in unexpected ways. Services such as Music Glue and TopSpin have pioneered "direct-to-fan" marketing, which allows artists to sell music, tickets, and merchandise directly to their fans from centralized online marketplaces.

This has meant major shifts in the industry. The nature of music marketing is changing, capital is flowing more freely into musicians' pockets, and artists are conceptualizing themselves as businesspeople (in addition to musicians) who are in the business of selling T-shirts and other paraphernalia as much as they are in the business of selling records. It's a win-win: By cutting out price-gouging middlemen, artists are able to reap higher profits and reduce costs for their fans.

2) The death industry.

The U.S. funeral market rakes in more than $20 billion each year while servicing an average of 2.4 million funerals annually. An average American funeral costs anywhere from $8,000 to $10,000 (up from an average cost of $706 in 1960).

Easily the biggest expense for most funerals is the casket, which costs an average of $2,300. That's because there's a huge markup on caskets sold in funeral homes: A casket that wholesales for around $300 may be sold at a funeral home for upwards of $1,300. For years, these costs were considered unfortunate but unavoidable.

All that is changing thanks to e-commerce, which has reduced casket prices to unprecedented levels. Some brands sell coffin kits online for as low as $600, while startup Willow and Werth offers fully built caskets starting at $775. Meanwhile, retail giants such as Costco and Walmart have started selling lower-priced caskets online. The diversification afforded by e-commerce has provided customers with an array of significantly more affordable options.

3) The alcohol industry.

In the past, alcoholic beverage companies were distanced from consumers by a three-tier distribution system that required beverages to pass from their creators, to wholesalers, to retailers.

These days, services such as Drizly allow users to shop local stores on a mobile device and order beer, wine, or liquor to be delivered straight to their home. Services such as Last Bottle eliminate the liquor store entirely by shipping wine directly from wineries and other suppliers to consumers.

This e-commerce disruption has required producers to focus more on distinguishing their products from the sea of available options. More attention is being paid to branding at the producer level (not just in retail stores). It's a response to the fact that e-commerce is dramatically changing the alcohol sales landscape: In 2015 alone, alcohol delivery generated $2 billion in revenue.

4) The grocery industry.

This might not seem surprising at first, since grocery delivery services such as Fresh Direct have existed in urban centers for years. What is surprising is that few analysts thought the $600 billion food and beverage industry would ever be truly disrupted by the rise of e-commerce. We can't really blame them: As recently as 2015 a measly one percent of food and beverage sales took place online.

Less than two years later, those analysts need to eat their hats. Both small tech startups and gigantic corporations (such as Amazon) have started investing in grocery e-commerce infrastructure, and specialty grocers are finding great success online. This momentum is driving the unprecedented annual growth of online grocery sales, which are expected to hit $18 billion in 2018.

To understand just how shocking this growth rate is, consider that offline grocery sales are expected to grow at a rate of 3.1 percent over the next year. Meanwhile, online grocery sales are projected to grow by 21.1 percent over the same period.

The takeaway here? Virtually no industry is immune from the e-commerce boom. All it takes for the tide to turn is for a few enterprising minds to identify an opportunity and execute it well enough that both consumers and established brands sit up and take notice. From alcohol to caskets, that's exactly what is happening in each of these industries.