Sleep, the primary architect of your child's brain
There's a persistent misconception that babies who sleep little are alert, lively, and curious babies. The neurobiological reality is quite different. Sleep is not a pause in your child's development; it is one of its most powerful drivers. From birth to three years old, during those hours when your baby seems simply absent from the world, their brain is doing considerable work.
Understanding what happens during sleep means better supporting your child through their nights, without anxiety, without contradictory injunctions, but with solid landmarks rooted in developmental neuroscience.
What neurons do during sleep
A newborn's brain contains approximately 100 billion neurons, but what will determine their future capabilities is not so much their number as the quality of the connections that will form between them. These connections, called synapses, build at a spectacular rate during the first three years of life: up to one million new connections per second in certain brain areas.
A large part of this synaptic consolidation work takes place precisely during sleep, and more particularly during REM sleep, which is particularly abundant in infants. A newborn spends about 50% of their sleep time in REM phase, compared to 20% in adults. This is no coincidence: it is during this phase that the brain sorts, consolidates, and integrates the day's learning.
Memory is built at night
Studies, notably by Rebecca Gómez's team at the University of Arizona, have shown that six-month-old babies who nap after being exposed to new language patterns retain this information significantly better than those who remain awake. Sleep therefore plays an active role in memory consolidation, long before the child can speak or express what they know. This link between sleep and language also echoes the observations developed in our article on language development and first words.
Cleaning and repair: the role of the glymphatic system
More recently, research by Maiken Nedergaard at the University of Rochester has highlighted the existence of the glymphatic system, a brain drainage network that activates primarily during deep sleep. This system eliminates metabolic waste accumulated by neuronal activity. In young children, whose brains are particularly active, this nocturnal cleansing is of paramount importance for long-term brain health.
Baby sleep cycles: understanding to stop fighting
Baby sleep is not like adult sleep, and this difference is often a source of misunderstanding. An adult sleep cycle lasts about 90 minutes. A newborn's lasts between 45 and 60 minutes. Between two cycles, the baby goes through a phase of semi-wakefulness during which they may cry, fuss, or seek reassurance. This is not a complete awakening, but a normal transition.
Many parents interpret this moment as a problem to be solved, a failure in sleep organization. But this particular architecture of infant sleep is functional: it allows the baby to regularly check the presence and availability of their attachment figures, which is consistent with their deep developmental needs. The link between these needs for nocturnal security and the construction of secure attachment is essential, as we explore in our article on emotional regulation in babies from 0 to 3 years old.
Changing needs with age
Sleep needs vary considerably over the first three years. A newborn sleeps between 14 and 17 hours per 24-hour period, divided into many short cycles. Between 3 and 6 months, a gradual organization begins to take shape, with a progressive consolidation of night sleep. Between 1 and 3 years, the child needs 11 to 14 hours of sleep, usually including one to two daily naps which gradually reduce to just one.
These figures are averages, not absolute norms. Each child has their own chronobiology, influenced by their temperament, environment, and emotional history.
The sleep environment: what neuroscience teaches us
The Montessori approach to sleep starts from a simple principle: the child needs a space that belongs to them, that they recognize, that sends them signals of security. The predictability of the environment plays a direct role in the level of cortisol, the stress hormone, which when chronically elevated, interferes with sleep quality and with the development of brain structures related to emotional regulation, particularly the amygdala and prefrontal cortex.
Regularity of rituals
Bedtime rituals are not arbitrary habits. They constitute sensory and emotional anchors that prepare the brain for the wake-sleep transition. Dimmed light, a calm voice, the same sequence of actions: bath, feeding, story, lullaby. The infant brain is a pattern detector. The more constant the signals preceding sleep, the smoother the transition becomes and the less resistance it involves.
The bath time, in particular, has a dual function: the drop in body temperature that follows immersion in warm water physiologically induces sleep, while also offering a moment of contact, play, and bonding. This is why choosing a suitable, stable, and comfortable bathtub, which allows this ritual to unfold peacefully, is not an insignificant detail. The Treelys foldable bathtub with stand was designed precisely to make this moment safe: ergonomic support, enveloping position for the baby, practicality for the parent, so that the evening ritual is a soothing experience rather than a source of logistical tension.
What neuroscience says about co-sleeping and separate rooms
The debate around co-sleeping is often presented as a cultural or philosophical choice. It is also a neurobiological question. Research by James McKenna, anthropologist and specialist in maternal sleep at the University of Notre Dame, has shown that physical proximity between parent and infant regulates the baby's breathing, body temperature, and sleep cycles. This co-regulation is particularly marked in the first months of life.
However, there is no universal answer. What matters is that the sleep environment, whether it's a safely arranged parental bed or a child's own space, is consistent, safe, and respectful of the child's temperament and the family's actual capabilities. Guilt, whatever the choice made, is the worst enemy of sleep for the entire household.
Difficult nights: when to worry, when to persevere
Sleep regressions are periods, often predictable, during which a child who was sleeping well starts waking up frequently again. They generally occur around 4 months, 8-10 months, 12 months, 18 months, and 2 years. These moments coincide with major developmental leaps: acquisition of object permanence, first attempts at walking, language explosion, emergence of self-awareness.
This is not a setback: it is an indicator that the brain is hard at work. Understanding these regressions as signals of progress rather than educational failures profoundly changes the way we go through them. These upheavals are intimately linked to the major developmental stages described in our article on your child's first 1000 days.
What truly helps
Several elements have documented efficacy in improving a child's sleep quality without coercive methods: consistency of rituals, reduction of light and sound stimulation in the two hours before bedtime, emotional stability of the parent at bedtime, and gradual transitions. This last point is central: the immature brain of an 18-month-old child cannot handle abrupt changes. Slowness and consistency are therapeutic tools in themselves.
Caring for sleep means caring for the bond
Your child's sleep is not a matter of time management or household organization. It is a window into their inner development, their emotional needs, and how their brain integrates the world. Supporting their nights with attention and kindness means offering them the optimal conditions for everything they experience during the day to transform, at night, into skills, memories, and confidence.
The Treelys philosophy starts from this observation: seemingly ordinary moments—the evening bath, the song repeated for the hundredth time, the hand placed on their back—are the foundational acts of development. No gadgets, no miracle solutions. Just the right presence, truly useful objects, and an understanding of what is actually happening in that small, developing brain.
