From computer vision to palm recognition to scan-and-go, technology intended to make it faster and easier for shoppers to pay for their purchases has recently taken center stage for retailers.

Self-checkout has taken on an especially high profile as retailers grapple with how to prevent people from neglecting to scan items and as shoppers air complaints about the systems, which many describe as annoying and difficult to interact with.

In a move that could help counter shopper ire, Target announced earlier this month that it will add express self-checkout stations to most of its stores and limit the number of items people can take through the lanes. Walmart, meanwhile, has added buy now, pay later as a payment option for customers using its self-checkout stations.

Scan-and-go technology has also made strides, with Sam’s Club announcing that about a third of its members use the checkout solution regularly.

Grocers are also looking to use smart shopping carts to personalize the shopping experience by presenting customers with customized offers as they walk around the store. Instacart, for example, announced in January that it is working with CPGs including General Mills and Del Monte Foods to serve up advertisements on its Caper Carts based on customers’ shopping behavior. Retailers will collect a portion of the revenue the ads generate.

Fully automated systems that use AI-driven cameras to allow shoppers to simply walk out of the store with their purchases have also grabbed attention in recent months, as Aldi has started using the technology from computer vision startup Grabango at a store in the Chicago area.

Here’s a look at some of the checkout-related stories that have made headlines over the past several months.