Our brains are split into two halves, a left hemisphere and a right hemisphere. While the left brain specializes in languages, the right brain specializes in faces. But the two halves don’t exist as two separate entities. Instead, both halves or hemispheres are connected at several points. These connections are important to transfer and coordinate information between hemispheres. But how do the correct neurons “know” if and where they should cross? The textbook model so far has described a positive chemical signal called Netrin that diffuses in the developing brain and guides crossing neurons. But new approaches to this question recently suggested a very different answer.