Crossing to Belgium from the Netherlands and back is simple. Just walk right in.
Although the two countries differ in policy, they agree on a free flow of migrants between them. No passport required and no border security to hold you. In fact, both countries allow EU and non-EU citizens to cross the border without delay (given that they have the legal paperwork). This part of the EU is known as the Schengen Area.
Not all EU member-states are part of the Schengen Area. The U.K., for instance, isn't part of the Schengen Area, so entering and leaving the country are still subject to passport checks. The entire EU mainland, however, is part of the Schengen Area, as well as non-EU countries such as Switzerland, Norway, and Iceland.
The Schengen Area is great for people who frequently move across Europe. They can settle in a Schengen country and operate virtually anywhere without being delayed by passport checks and border security. In fact, one of the primary purposes of establishing the Schengen Area is to promote free trade.
Thanks to the Schengen Agreement signed in 1985, The Dutch-Belgian border has become one of the most interesting borders in the world. The border can actually divide a house's living room and kitchen. EU and non-EU tourists come to take their picture standing on or in between the border, which is marked by a series of plus signs.