Retail giant Walmart announced this week a first-of-its-kind investment in an indoor vertical farm. The Series E investment of $400 million is going to San Francisco-based Plenty Unlimited Inc and the long-term agreement means Walmart will source Plenty’s leafy greens for its California customers later this year. Plenty’s indoor farming structure can quickly grow multiple crops on one platform while reducing transportation and food waste. The company also uses 100% recyclable packaging.

Plenty says vertical farming is a new era of agriculture that allows consumers access to fresh, healthy greens year-round, regardless of location. Walmart’s significant investment is the first time a large U.S. retailer has invested in vertical farming.

Read more on Plenty’s vertical farming structure and Walmart’s investment here.