the synaptic plasticity, which is the basis of remembering and learning in the brain. [1] However, not all the functions discovered in biological synapses have been realized on single artificial synaptic devices with energy consumption of femto-Joule per event, which has limited the building of neuromorphic computing systems. [2,9] Organometal trihalide perovskites (OTPs) including methylammonium lead iodide (MAPbI 3 ) have recently emerged as a new generation of earth abundant semiconductor materials for solar cell applications, [10][11][12][13][14][15] which have demonstrated a high certified efficiency over 20% [10] due to their superior optoelectronic properties of strong absorption, [16] unusual defect physics, [17] extremely low trap density, and long carrier diffusion length. [18] Besides, they have also been demonstrated for applications in other electronic devices, light emitting diodes, [19] laser, [20] photo detectors. [21] In this work, we demonstrated low-temperature, solutionprocessed two-terminal MAPbI 3 devices as ideal candidates of memristors and synaptic devices to mimic the biological synapses. The twoterminal OTP synaptic devices can mimic the neuromorphic learning and remembering process. Many functions of biological synapses have been visualized in the perovskite synaptic devices including four forms of spike-timing-dependent plasticity (STDP), spike-rate-dependent plasticity (SRDP) short-term plasticity (STP) and long-term potentiation (LTP)), and learningexperience behavior etc. The perovskite synapse has potential of low energy consumption of femto-Joule/(100 nm) 2 per event due to the switchable p-i-n structure and low activation energy for the ion migration in OTP material. [22] A novel phenomenon of photo-read SRDP was observed, which offer a novel readout method using light in addition to the electric pulse. Figure 1a shows the structure of the device with perovskite layer sandwiched between two electrodes poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) covered indium tin oxide (ITO) and gold (Au), which have comparable work functions. PEDOT:PSS is considered as an anode and Au as a cathode for the simplicity of following discussion. It is a typical metal-semiconductor-metal (MSM) structure New parallel computing architectures based on neuromorphic computing are needed due to their advantages over conventional computation with regards to real-time processing of unstructured sensory data such as image, video, or voice. However, developing artificial neuromorphic system remains a challenge due to the lack of electronic synaptic devices, which can mimic all the functions of biological synapses with low energy consumption. Here it is reported that two-terminal organometal trihalide perovskite (OTP) synaptic devices can mimic the neuromorphic learning and remembering process. Various functions known in biological synapses are demonstrated in OTP synaptic devices including four forms of spike-timing-dependent plasticity (STDP), spike-rate-dependent plasticity (SRDP), sh...