Mapping mammalian synaptic connectivity has long been an important goal of neuroscience because knowing how neurons and brain areas are connected underpins an understanding of brain function. Meeting this goal requires advanced techniques with single synapse resolution and large-scale capacity, especially at multiple scales tethering the meso- and micro-scale connectome. Many types of questions in neuroscience require detecting and mapping synapses in the complex mammalian brain. A new tool, mammalian GFP reconstitution across synaptic partners (mGRASP), offers a relatively easy, quick, and economical approach to this technically challenging task. The mGRASP method is suitable for mapping mammalian synaptic connectivity at multiple scales: micro-scale for synapse-by-synapse or neuron-by-neuron analysis; and meso-scale for revealing local and long-range circuits. The increasing pace of technology developments for neuroanatomy called connectome make us feel that it is indeed exciting time to be a neuroscientist witnessing our steps towards keys to unlock the mystery of the brain.